Another thing I do, which isn't the same as having intellectually-matched peers, but is better than just hanging out with mommy all the time, is use teen babysitters (a couple of them have been homeschooled). I'm a doctoral student, and when dd was little I worked very part-time, so I've had teens come for a couple/few hours several/every day of the week. Lets me get what I have to do done, mixes things up for her; more expensive (per hour) than day care, but not prohibitively so.
Speechie -- I wish you luck with PreK next Spring. DD was in daycare for about a year, and she did fine, but since I've taken her out, she's just bloomed and is now SO different from her age-mates, which sounds like how things are with your DS. I cannot imagine putting her in PreK now (partly because I share JJsMom's frustration re immaturity).
