In reply to Cragchick:
I am a little less well endowed than you, but still need serious support when running - less so when climbing. I think you really need to go and try them on because brands aren't consistent with sizing - I am a 30E in certain regular bras but a 32DD or even a 34 in sports bras, so you may need to go up a band size from normal. I have some Shock Absorber ones designed for tennis players, I think, that squish things down a lot. Some runners who have bigger boobage than me either wear two bras, one bra and a crop top, or a terrifying contraption from an American company called Enell (as in F' Enell they're big, perhaps?) who make something that looks hideous but is apparently effective.
Sports bras come in two types, or a hybrid: compression, which squash things down and together, and can create a uniboob, and encapsulation, which holds each one apart, so potentially more flattering but less flattening
Try Rigby and Peller, or Bravissimo. There is also
http://www.lessbounce.com/ but I think if it wasn't a bra I was already familiar with, I would need to order a 3x3 matrix of cup and band sizes and send 8 of them back, which seems a bit extreme