You're not in danger if you just get oral sex. Even if the other person is HIV+, AIDS, or is not on medications unless you have a cut down there you will not get it. That's what gay male friends of mine have said when they told me how they had safe sex with men who are HIV+ or who had AIDS.

You can however get lots of other STDs.

http://www.sfcityclinic.org/stdbasics/stdchart.asp