1. Don't. 

2. Do it with an E-card. Yes, an E-card. InSPOT.org, a California based non-profit, allows users to send a free, anonymous E-card to their partner(s) telling them they might want to get tested for STDs such as HIV, gonorrhea, chlamydia and syphilis. Potential messages?

"You're too hot to be out of action. I got diagnosed with an STD since we played. You might want to get checked too."

My personal favorite--"I got screwed while screwing--you might have too. Get checked for STD's"
 

Or the significantly less exciting--"I'm so sorry. I didn't know I had STD's when we were together. You should get tested."

InSPOT also offers locations where one can get tested, as well as the potential to seriously ruin someone's day.

Ways NOT to get back at that douche who never called you back? Anthrax. Ways to totally do it? inSPOT.