You can test for NGU, chlamydia and gonorrhea now, and those are the ones that are most likely to cause the symptoms you've described in your other post. (And lets keep everything to this thread, since its easier for us to keep up with that way.)
Syphilis is 6 weeks, HIV is 3 months, and herpes is 4 months, though most people test positive sooner for all of those.
AJ
From what I am reading and seeing, it appears that the wait time varies from 3-4 days to about 6 weeks. Except HIV which might be longer. Someone can correct me if I'm wrong but a 3-4 week wait will detect most stds. And get tested earlier if you have symptoms. There are some other good posts on here about this, particularly from the Doctors you may want to check out in the expert section. Good luck.