My Under Armour Ts I just wash cold and tumble dry along with the rest of my laundry.

Same goes for my many various knickers (Chrome, Swobo, Swrve, etc) and all my cycling socks, wool or otherwise.

Wool tops I wash cold and hang dry in the bathroom. I do the same thing with all my cycling caps and my various pieces of squid-wear (jerseys, padded knickers, tights and shorts).

I wash most everything I have once every week or two. The big exception is my heavy wool Swobo knickers... which I've never washed.

I just got my first waterproof cycling layer that I actually like and breathes well enough that I can use - a Cutter Cyclical eVent jacket - and supposedly they do need to be washed pretty often to maintain their waterproofness. I plan on using some Nikwax (which I already have), cold washing it, and letting it hang dry.