I use Hoya HMC UV(O) (46mm@$30) and Hoya HMC UV(C)/UV(O) (52mm@$20). The 46mm is harder to come by. Check with MScolor. Don't ask what is the difference between UV(O) and UV(C) as there appears to be different answers but none authoritative.
Yes, the lens cap and/or lens hood can be used w/o having to remove these filters. These UV filters are meant more for protecting the lens when the caps are off for those walking shoots rather than for their 'cutting through haze' or 'UV' abilities.
Hoya has a long tradition in making filters. Their HMC UV filters have also been compared favourably (good value, low image degradation) with other similar filters.