I have noticed the same problem. I didn't notice it the first few months I started using dri-fit workout gear exclusively, but then it got to a point where my wife almost became nauseous any time she walked into our laundry hamper area. I like the way the clothing fits, hangs on me, looks, etc., but am about ready to toss it all if I'm going to stink to high hell after I work out in it.
I experimented earlier this week by washing it all on a "sanitary" cycle in our front-loading washer. It super heats the water to a level that should kill any residual bacteria on clothing. I do want to mention that the clothing smells fine AFTER I wash it, no matter what cycle I put it on (using Tide and Downy softener). The problem is after I work up a good sweat with 20-30 minutes of cardio and some weights. It stinks until I can get it in the wash.
Just this morning I wore a pair of old shorts and a t-shirt (both all cotton) and absolutely no odor (according to my wife) when I got home.
I read some of the answers above about special washing procedures, etc., but even if they DO work I don't want to deal with the stink of the clothes until I get a chance to wash them. It's not realistic to wash them immediately after I get home.
I guess Goodwill is going to get a lovely donation of about $300 worth of dri-fit workout clothing.