I was a 34C pre-pg (they're large & in charge now...), and my best luck with sports bras were the Champion Seamless, mostly because they layer under another supportive top really well. They're not going to get you through a marathon on their own or anything ;-)
I have a reversible Brooks bra that was great, too, and just got one from Patagonia (the Capilene fabric -- pullover styling with a back hook for extra support) and it is SO COMFY, and cute, and supportive.
An anti-recommendation is Under Armour. I bought one of their sports bras and within a few wearings it was falling apart at the seams. Literally. Total crap.