Might also want to add MassAmmo and get on their e-mail list. Around holidays they can offer some very good deals. Last purchase I made was 420rd M193 in cans for $138 delivered.
Play with this one, I do. Makes finding ammo/parts/firearms/deals like going to a gun store flea market. I found this up in the sticky, made wikiarms my homepage... ugh. Can't stop spending money.
For free shipping by the case check out Target Sports USA. For instance, right now they have Seller and Belot 9mm 115gr. 1000 rounds for $199.80 with free shipping
SGammo is also great and although they don't have free shipping their combined price is within a dollar or two of Target Sports USA.
Freedom Munitions is another good one although they mainly do remanufactured
+1....Ive bought many cases from TS. Also Ammoman. Somethings high but most are good deals.
All good suppliers listed in this thread (cept CTD )