[Galaxy Ace S5830i Android Development] El_Dark:
I thought it may come in handy, the list sorted by colour and alphabetical order according to each colour

RED

AccountAndSyncSettings.apk

Helps to sync with google servers in order to recognize your google account.

AlertRecipients.apk

Unknown Function

ApplicationProvider.apk

Fetches list of applications installed on the phone to provide search suggestions in Market application.

AxT9IME.apk

Samsung Keyboard, can be replaced with a modded keypad.

BadgeProvider.apk

Notifies about the no. of sms and calls on respective icons in dock on launcher.

BluetoothOpp.apk

Bluetooth App

BluetoothPbap.apk

Bluetooth App

BluetoothTestMode.apk

Bluetooth App

BrcmBluetoothServices.apk

Bluetooth App

Calendar.apk

Calendar Application, can be replaced with other calendar application from market.

CalendarProvider.apk

Calendar Sync with KIES, ONLY DELETE IF YOU ARE NOT GOING TO USE CALENDAR AT ALL.

CertInstaller.apk

Certificate Installer, if removed WiFi won´t work

ContactsProvider.apk

Contacts Sync with KIES.

CSC.apk

Country Specific Codes, controls APN settings...

DataCreate.apk

If deleted will cause Bootloop, Unknown Function.

DefaultContainerService.apk

For installing apk files through the phone, unknown applications or non-market ones.

DialerTabActivity.apk

Phone Dialer, can be replaced with modded version.

DownloadProvider.apk

Handles download files, i.e Market, Browser, Direct Downloads.

DownloadProviderUI.apk

Complement of DownloadProvider.apk

DrmProvider.apk

DRM Functions, i.e accessing media files like photos, videos, music, etc.

DrmUA.apk

For music playback.

FactoryTest.apk

Factory Test, test if everything works fine.

fotaclient.apk

Firmware Over The Air Download, instead of using KIES it downloads firmware update directly to phone.

GoogleBackupTransport.apk

Backup Apps and Settings from your phone to Google Account.

GoogleCalendarSyncAdapter.apk

Calendar Sync with Google Account.

GoogleContactsSyncAdapter.apk

Contacts Sync with Google Account.

GoogleFeedback.apk

Force Close Reporting to Google in order to help fix problems in next firmware update.

GooglePartnerSetup.apk

Helps to set Google Account with the phone.

GoogleServicesFramework.apk

Provides account / login information to Google Applications.

InputEventApp.apk

Unknown Function

JobManager.apk

Task Manager, can be replaced with ported version from another device.

LogsProvider.apk

Displays call logs in the dialer.

MarketUpdater.apk

Complement of Vending.apk, helps to update applications installed through Market.

MediaProvider.apk

Accesing Media File i.e images, music, files, etc.

MediaUploader.apk

For uploading media to remote servers, uploading attachments in emails, third party pages as mediafire dropbox.

MmsProvisioning.apk

Provide Mms/Sms Services.

MobileTrackerEngineTwo.apk

Tracks Phone when stolen, part of Samsung.

NetworkLocation.apk

Provides Cellphone services

PackageInstaller.apk

For manually installing apps, i.e Non-Market Apps. Part of DefaultServicesContainer

PCWClientS.apk

Unknown Function

Personalization.apk

Unknown Function

Phone.apk

Phone Application.

PhoneErrService.apk

Unknown Function

PhoneSky.apk

Related to Vending.apk, if you don’t have vending.apk this will install it automatically. Can be Google Play depending on firmwares.

PictoTts.apk

Text to Speech Translator.

PopupuiReceiver,apk

Unknown Function

PowerOnOffTest.apk

Unknown Function

Preconfig.apk

Phone Configuration.

SecDownloadProvider.apk

Unknown Function

SecurityProvider.apk

Unknown Function

SelfTest.apk

Unknown Function

SerialNumberLabelIndicator.apk

Unknown Function

serviceModeApp.apk

Uknown Function

Settings.apk

Settings Application.

SettingsProvider.apk

Part of settings.apk

SetUpWizard.apk

Set Up for first time loading, language, accounts, time, zone, etc.

ShareApp.apk

Sharing Media Files through Gallery

signin.apk

Samsung Account

SisoDrmProvicer.apk

Music Playback

SnsAccount.apk

Accounts Sync Facebook, Twitter, etc

SnsProvider.apk

Part of SnsAccount.apk

Stk.apk

Sim ToolKit, if delete may cause problems with data and phone service

syncmldm.apk

Software Update

syncmlds.apk

Samsung Account

SystemUI.apk

Android User Interface

TelephonyProvider.apk

Phone Services

VpnServices.apk

Connects to VPN

wssomacp.apk

Mms/Sms Notification

wssyncmlnps.apk

Needed for Syncing with KIES

Vending.apk

Market Application.

ORANGE

Browser.apk

Browser Application, can be deleted if replaced with another browser i.e Opera, Chrome.

Calculator.apk

Calculator Application, can be replaced with modded version.

Camera.apk

Camera Application, can be replaced with modded version or from other device if ported.

Contacts.apk

Shows your contacts on phone or sim, also displays logs in dialer.

Mms.apk

Mms/Sms Application, can be deleted if your replace with another app i.e go sms.

Music.apk

Music Player. Can be deleted if replaced with another music player.

MyFiles.apk

My Files Application. Can be delete only if replaced with similar application.

SamsungAppsUNA3.apk

Part of Samsung Apps, DELETE ONLY if you deleted SamsungApps.apk.

Street.apk

Street View, part of maps.apk. DO NOT delete if you use Google Maps.

Talk.apk

Google Talk Application. DO NOT delete if you use Google Maps or Google Translate.

TouchWiz30Launcher.apk

Touchwiz 3.0, can be deleted if you have another Launcher installed i.e Holo Launcher, ADW Launcher, etc.

GREEN

ClockWidget.apk

Clock Widget.

Deskclock.apk

Clock Application.

Dlna.apk

All Share Application.

DualClock.apk

Dual Clock Widget

Email.apk

Email application, you can always download your desired application i.e Yahoo Mail, Gmail, Hotmail.

EmailWidget.apk

Email Application Widget

FmRadio.apk

Fm Radio Application.

Forest.apk

Live Wallpaper.

Gallery3D.apk

Gallery Application, can be replaced with other applications such as QuickPic.

GenieWidget.apk

News and Weather Widget.

GoogleQuickSearchBox.apk

Quick Search Box, for searching information inside the phone such as text files, image, etc.

HTMLViewer.apk

View Html Codes.

lcdtest.apk

LCD Test

LiveWallpapersPick.apk

Live Wallpaper Picker.

Maps.apk

Maps Application.

Memo.apk

Memo Application, can be replaced with similar application.

Protips.apk

System Tips

SamsungApps.apk

Samsung Apps

SamsungWidget_ProgramMonitor.apk

Program Monitor Widget

SamsungWidget_StockClock.apk

Yahoo Finance Widget

ScreenCaptureService.apk

Makes Screen Shots

Swype.apk

Swype, writting input method. Delete only if you dont use this method.

thinkdroid.apk

Office Application, can be replaced with another application.

TtsServices.apk

Text To Speech, part of Maps, Google Translate. DO NOT delete if you use Google Maps or Google Translator.

TwWallpaperChooser.apk

Touchwiz Wallpaper Selector

UnifiedInbox.apk

Social Hub Application

UserDictionaryProvider.apk

Dictionary for Latin IME Keyboard

VoiceRecorder.apk

Voice Recording

VoiceSearch.apk

Voice Search for Google Search, Google Maps

wipereceiver.apk

Wipes device remotely if stolen, part of Samsung. Its your choice, either keep it or delete it.

WlanTest.apk

Test Wlan Connectivity

Youtube.apk

Youtube Application.

HTH to make it a bit simpler :)

PS: What are the Launcher*.apk packages for?

Example, I have:

LauncherAlarmClock

LauncherBrowser

LauncherCalendar

LauncherCamera

LauncherContact

LauncherDownload

LauncherEmail

LauncherFmradio

LauncherGallery

LauncherMessage

LauncherMusicplayer

LauncherSettings

LauncherStk

More to the "Unkown" list:

Talkback.apk

framework-res.apk (This one is not actually unkown, but someone who doesn't know might commit the mistake of erasing it... it is

Spoiler content hidden.