Applications I use
A more up-to-date list of Android applications on my phone is over on AppBrain.com.
Replacing Gallery3D with Gallery (2D version)
Android 2.0 and above (and their respective Cyanogen ports) replace the Android's original 2D Gallery application with a fancy one (known as Gallery 3D) with whiz-bang 3D graphics.
Unfortunately, it's painfully slow on devices like the T-Mobile G1 (aka HTC Dream) and T-Mobile MyTouch 3G (aka HTC Sapphire/Magic). However, if you've rooted your phone, you can remove the 3D version of the app and replace it with the 2D one, which is significantly faster.
Download the 2D version of Gallery: Gallery.apk