Get on the NewEgg Auto-Notify lists for every card you see. If you get email to your phone, that helps. I loaded a search for the 5870, and 5850 on my PC at work and hit refresh every 5-10 minutes. The first day I tried to buy one and when I clicked the ADD to CART button it said it was out of stock. The 2nd day there as an ASUS in stock and was able to get it. You just have to watch it like a hawk.
I had an ultra-rotten experience with Tiger Direct selling me an item that was listed as being "in stock" After I placed my order and after they put a $600 hold on my credit card, they said my order would ship in 2-3 weeks. WHAT?!? If it's in stock and I have proven I can pay for it, why wait 2-3 weeks? That was such a dishonest thing to do I canceled my order (very painful process) and have never ordered from them again. Maybe my bad experience was an isolated one, but unless they're a healthy amount cheaper than other sources I will not be ordering from them again.
I bit the bullet and got a XFX - ATI RADEON HD 4850 from best buy as all my parts came today, and when a 5870/50 come in I'll buy that too and Crossfire them.
Note: REALLY REALLY DUMB! waste of 100 bucks. First off, you cant crossfire a 4850 with a 5850. Second, you didnt have to buy a 4850 which is a descent card. Since it's only temporary you couldve spent like 50 bucks on a 4670 or something else... Also you shouldnt just buy the one that becomes available first! There's a pretty big difference between a 5850 and 5870. If you have the money to get either, just be patient and buy a 5870...