NBA League Pass is really good if you can afford the £60. Great quality and you get every single NBA game (and the ability to watch it again for 24 hours). The address is
Welcome - NBA League Pass Broadband.
Also, for non-live stuff there are two great sites I found-
BBALLVIDEOS - Coverage Of The 2009 Eurobasket - says Eurobasket but it actually has everything NCAA/NBA/Euro (use firefox and download the 'skipscreen' add-on to get around megaupload)
MixMakers.net