Techwick line. I have one of their Lightweight Crews T1, and a pair of their Heavyweight Long Underwear Tights T3. The crew is great as a base layer for running, hiking, an extra layer for winter sports, etc. I got the T3 tights for running in winter (I don't run anymore), as well as winter sports (snowshoeing, skiing/boarding, x-country, etc).
I'll be posting more about great gear websites soon. Also, look for posts on winter sports.