Steve has just released a pair of boxers at Poserworld (subsctiption) that are pretty neat. He's also working on a pair of tighty-whities to be released soon (I have no idea on how soon). rDNA also has a set of underware, tight boxers and t-shirt. There's a jock strap here by Eezee that's really nice, either as a stand alone or as part of his Leather Pack for Mike. Over at the Penguinbar there's a free jackstrap prop and a g-string. The catsuit for Mike can hide everthing except the briefs so it looks like underware. The standard one is at Daz, and there are remaps for it for easier texturing. PoserStyle also has a catsuit (subscription), but they're having problems right now with their site so you'd have to contact them via email to get it. You can also use one of the subdividing mat poses available here and make a quick texture of your own. Or you can pose Mike, and add a pair in postwork by painting one on from a photo. I think those are all the options. Anyone think of anything else?