[Captivate Android Development] kennethpenn:
Here you go! Ripped straight from my article: How To: Remove AT&T From Captivate.

Instructions

WARNING: I am not responsible for any bricked, messed up, ruined devices. You modify your phone at your own risk. These processes are not necessarily safe for your Samsung Captivate or any other device.

Root the Samsung Captivate

First things first. You’ll need to root your device to continue with many of the modifications listed below. For our “How to Root the Samsung Captivate” guide, click here. It’s very very easy. Even a total noobie can do it! If you have questions, post a comment and we’ll get back to you A.S.A.P. Look below if you get the idea, check out our “How to Root the Samsung Captivate” guide if you don’t.

Download Update.zip

Plug in your Captivate to your computer. When the phone notifies you that the USB has been plugged in, scroll down your notifications bar and click on “USB connected: Select to copy files to/from your computer.”

Click “Mount”

Now, you’ll probably see a popup telling you a new USB drive has been inserted, open it up on your computer. In Windows, click “Open folder to view files.”

Drag Update.zip into the Captivate USB drive (on the top level… do not navigate into folders)

Turn off the Captivate (Power Off)

Hold down the Volume Up/Down rocker and the power button until you see some action. Your phone is now booting into recovery.

Use the volume down button to scroll down to “Reinstall packages”

Click the power button to select that option

Enable App Sideloading

AT&T has some weird reservations against app sideloading. That means, AT&T Android users can not use any apps not downloaded on the Android Market. Have no fear! You can remove this restriction easily. Check below for the basic instructions, or click to go to our “Enable Captivate App Sideloading” guide.

BusyBox Installed

Samsung Captivate with root

SQL Database Manager

We suggest trying the SQLite plugin for Firefox, you can find it here.

Turn on USB debugging: Settings >> Applications >> Development

Plug in your Samsung Captivate

Open up Command Prompt on your computer (Windows: start, search, type “cmd”, right click cmd, Run as Administrator)

Type in: cd _____PATH TO ANDROID SDK FOLDER______\tools

Example: cd C:\Users\USERNAME\Desktop\android-sdk-windows\tools

Type in: adb shell

Type in: su

Type in: cp /dbdata/databases/com.android.providers.settings/settings.db /sdcard/settings.db

Type in: cp /dbdata/databases/com.android.providers.settings/settings.db /sdcard/settings.db.backup

Type in: exit

Type in: exit

Type in: adb pull /sdcard/settings.db %userprofile%\desktop

Leave Command Prompt open

Open SQLite Manager in Firefox by pressing Tools >> SQLite Manager

Click “Database”

Then click “Connect Database”

Navigate to “settings.db” on your Desktop

Expand the tables

Click “Secure” on the panel

Scroll down to ID 6, “install_non_market_apps”

Double click it and change “value” from 0 to 1.

Close SQLite Manager

Go back to the command prompt window, type in: adb push %userprofile%\desktop\settings.db /sdcard

Type in: adb shell

Type in: su

Type in: cp /sdcard/settings.db /dbdata/databases/com.android.providers.settings

Type in: chmod 777 /dbdata/databases/com.android.providers.settings/settings.db

Type in: reboot

Disconnect your Captivate from your computer while your phone reboots.

Remove AT&T Bloatware Apps

Must have root and BusyBox installed before performing this process!

Open up Android Market and search/download “Titanium Backup”

Make sure your phone is not “Mounted” with USB

Open Titanium Backup

Press the Backup/Restore button

Click on each app and press un-install if you’d like to get rid of it. Do not delete apps off of this list, unless you know it is safe! This deletes these potentially forever… so be sure about things!

Delete-able:

AT&T Navigator

AT&T Radio

AT&T Maps

AT&T Music

AT&T Mobile Hotspots

Mobile Banking

Mobile Video

Where

YPmobile

AT&T FamilyMap

Mini Diary

MobiTV

Write and Go

Remove AT&T Market Restrictions

Market restrictions? What? You mean AT&T really censors what apps I can and cannot see on my Samsung Captivate? Yes they do. But, no problem. Android developer Andrea Baccega has developed an app called "Market Enabler" to remove the censorship by emulating the T-Mobile market on the Samsung Captivate as well as other devices. Instructions below if you've already got root access:

Download “Market Access” and install the latest version of the APK file on your Captivate.

Don't know how to install .apk files? Copy the file to your phone and then install "Apps Installer" or "Astro File Manager" from the market. It's easy! Just double click the .apk when you find it!

Close the Market down fully. If you were running the Market previously, reset the phone so it is not a running task. Or use a task killer and end the Market app.

Open up the Market Access application and go to "Backup value" in case you need to get back to the AT&T market

Then click "Providers" and find: "T-Mobile [US]"

Click and hold that option until it says "Emulate "T-Mobile" SIM?" -- click "Yes" there

You may have to Allow Market Access in Superuser Permissions

Click back to "Settings" click the checkbox next to "Emulate on boot"

All done. Now your Market is uncensored.

Remove AT&T and/or Samsung Logos on the Device

Not quite yet! Check back later. We are working with some chemistry-experts to see if we can dissolve those logos. Have you seen how sexy the Captivate is without logos? Click here to check out the video.

Credits

Big thanks to the XDA-Developers forum users for all their hard work on posting Captivate guides. User: nbs11 – bloatware removal. User: clubtech – market censorship removal application. User: blackjackboy – original root guide. User: kirbo20 – app sideloading.