Males can be tested for chlamydia and gonnorhea 2-3 days after possible exposure (pee in a cup). Most cases of syphilis (about 90%) will show up in blood tests after 6 weeks of exposure. HIV testing is now very reliable (but not always) after 6 weeks. Herpes usually shows up as sores within a week or two of exposure, and these sores can then be swabbed for testing. The standard blood tests for herpes are notoriously problematic (false positives/negatives, difficulty in interpreting results, etc), but can be done after a few months.
www.ashastd.org has info on std's for more reading to further educate yourself on std's, prevention, testing and treatment.
grace