[T-Mobile, Samsung Galaxy SIII] Woody:
Before we begin on the below, I must continue something about kernels from above due to character limits in posts.

A word of advice from vikas.mishra via XDA RD dorimanx in this post:

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Memory Management

Did you know that you can also free up some internal memory space by just basic maintenance? You can install a Cache Cleaner from the market. I use Cache Cleaner NG (root) and CacheMate (root) which will clear your cache for you, Cache Cleaner NG will even clear your cache on your SDcard. Open Root Explorer and if you see a bunch of free floating cache files, those need to go. Wasted space. Small in the scheme of your SDcard, but still wasted.

So here we go (best part is at the bottom though):

Ok so you go into XDA on your phone, go to the themes page and look at what and how people are theming their phones or see some pix of someone's SetCPU profiles. All those develop a cache that takes up space on your phone. Now lets say that you go to the market and look through some apps or update your apps (more on this later). This also generates cache, usually up to 2-4mb. Ever try to download something from the market and it says something like "not enough space". This not needed cache may be some of the reason.

Here are some tricks and apps that some of you may know and also some tricks that I have found that I am sure most don't know about.

SOME GOOD LOW MEMORY APPS:

Cache Cleaner NG and Cache Mate (both root and free-Cache Mate has a paid but the free one works just fine.)

Diskusage (free) ~ This one will show you a graphical version of your /data/apps and also you SD card to show you exactly what is taking up so much space. You can click on that item and hit "Show" and it will take you to the app's page in Manager Applications. It also has a root function too that will allow you to see what is in /system, /cache, /data,…

Some sort of file manager to get to some things I'll mention below. (I use Root Explorer)

SOME MEMORY CLEARING TIPS AND TRICKS:

Home Launcher ~ If you have a 3rd party home launcher, see if it has the ability to long-press an icon to take you to its screen in the Manage Apps section. I use APEX and if you long-press on say Market, it takes me to the same place as is I were to go to Settings->Applications->Manage Apps->Market. Instead of all that, just long-press on the icon and BAM! it takes you there. Here you can clear out your cache for the market or delete the data (if you need to do that). Or clear the cache of the XDA app b/c you looked at too many pix.

Browsers ~ These develop cache that takes up memory and space, especially the stock browser. If you use a 3rd party, you can get the settings to clear cache, cookies, passwords,…on exit. I use Dolphin, but I am pretty sure that most have something like this on them. (side note: most 3rd party browsers once exited will not run in the background unlike the stock one)

Media ~ So you download a bunch of mp3's from the net or click on some pix and save it to your SD card. Or maybe you just felt like wiping your card and having a fresh start. Every time you reboot, you phone will scan media. No big deal, but the more you criss-cross things from PC to phone and back again, it can create a bunch of double files in your media cache on the phone. With the proper placement of .nomedia files (this prevents your media scanner from doing just that, scanning media- i.e. pix, jpegs,…Don’t place a .nomedia in your music, album art or DCIM files**bad).

Every once in a while, I'll hit the Diskusage or go to Manage apps and clear the media cache. Then I got to my file manager and the DCIM->Thumbs and delete the .Thumbnails files (should be 2). Unmount the SD card and remount to start the media scan, pull up the Gallery and wait for the thumbs to come back (depending on how many you have, this could take awhile). By doing this you can get almost 5 mb back if you have a bunch of double scans in your media folder.

AND NOW FOR SOME TIPS THAT MOST COULD NOT KNOW:

LOSTDIR - Lets say that you have your phone plugged into your PC and for some reason you, in a fit of rage, jerk the plug out without unmounting it first. This creates a file that is put into your LOST DIR folder on your SD card. Anytime you don't safely unmount the SD card, it will create a file in that folder. In the scheme of the SD card, it isn't too much, but I don't like having useless items free floating about.

Here is a good explanation of what the Lost.dir is for, seems legit, I buy it.

TOMBSTONES - So you are downloading an update from the market and for some reason your phone freezes and the Force Close-Retry-Wait doesn't work out for you. You have to do a battery pull. Frustrating I know and the memory takes a hit too. Every time you have to do a battery pull because of a freeze up or something of the like, it creates a TOMBSTONE file in /data. These are useless and can be deleted. If you are flashing ROMs and are constantly having to do battery pulls b/c market crashes or an app freezes, then you are creating a Tombstone file.

**Here is where your file manager (with root) will help. Go into /data and scroll all the way to the bottom and open /tombstone. There should be some files in there and depending on how many there are, I could be a nice chunk of wasted memory. Just select all and delete. They are not needed. Your internal memory should go up by doing this.

LOST & FOUND - Same scenario, but now go into /data/ cache or /cache and you'll see Dalvik-Cache (don’t mess with this), Lost & Found and Recovery. If you tried to download an app and it got frozen for some reason and had to do a battery pull, the apk will be free floating in there, uninstalled (free floating radical). You can delete this. While it isn't in the Dalvik-Cache folder, it is taking up space. Once you are able to download something completely and correctly from the market, it will populate into Dalvik-Cache correctly and won't be a free radical, as I like to say.