Joel,
I don't know if these would be categories of tests or not but they would be useful IMHO.
Some way to specify the order in which tests are run within test suites. I think that right now, the tests I wrote that use the acs-automated-testing package are executed in the order in with they are defined in my test-procs.tcl script. (I don't know what order individual *-test-procs.tcl script files get loaded though. Probably best not to depend on this since you would want the scripts to be able to execute independently.)
For instance, if I have a test case that verifies that object_type_a can be created via database function and a tcl proc, I want to be sure this test runs before any other tests that create object_type_a's and run tests on them. Obviously if the an object_type_a can't be created, it'd be easier to glean that from the test results for the object_type_a creation test (and not other tests that do other things with the object).
Anyway, just some current thoughts that came up while trying to organize my tests...