RealBench is an application for benchmarking the file system. For now it has just one benchmark -- a benchmark that heavily stresses the file system for both reading and writing, as well as heavily stressing ram and the garbage collector. Basically, this is a benchmark designed to do as poorly as possible with the SGS's stock problems
StabilityTest is a stress-testing tool for android devices with error reporting. StabilityTest is a CPU and RAM/memory stress-testing tool like for your device, whether stock and unrooted (limited functionality)
TAP Benchmark - This app is aiming to give you better numbers for comparing different filesystems used in various lagfixes. It should also work for different phones, so that you can compare performance between them
Test Card - A very simple screen test card for Android. Designed to allow you to view the structures of pixels under magnification. On many phones this will be totally uninteresting; on some, notably AMOLED displays, it may be more useful. Please read the help for more info
Touch Test - Shows display parameters, multiple touch points, and trails to let you see how linear your touchpanel is. Different hardware supports 1, 2, or more fingers -- see which yours is. Note Android before 2.0 supported only single touch. Please see the help for more info