I second the i7 2600k...there's not a better chip for the price out there right now (except maybe for Ivy Bridge, but I haven't researched).
$315 Intel Core i7-2600K Sandy Bridge 3.4GHz (3.8GHz Turbo Boost) LGA 1155 95W Quad-Core Desktop Processor Intel HD Graphics 3000 BX80623I72600K
$225 ASUS P8Z77-V PRO LGA 1155 Intel Z77 HDMI SATA 6Gb/s USB 3.0 ATX Intel Motherboard
$100 CORSAIR Vengeance 16GB (4 x 4GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Desktop Memory Model CMZ16GX3M4A1600C9
As far as video goes, that board will support PCI Express 3.0, but for now, this should chew through anything you throw at it. You will have the ability to upgrade to a 3.0 card later.
$134 EVGA 01G-P3-1556-KR GeForce GTX 550 Ti (Fermi) FPB 1GB 192-bit GDDR5 PCI Express 2.0 x16 HDCP Ready SLI Support Video Card
$150 CORSAIR Professional Series HX750 (CMPSU-750HX) 750W ATX12V 2.3 / EPS12V 2.91 SLI Ready CrossFire Ready 80 PLUS SILVER Certified Modular Active PFC Power Supply
You'll definitely benefit from having an SSD as an OS drive. Traditional hard drives will be fine for your video storage drives and to edit from.
$160 Crucial M4 CT128M4SSD2 2.5" 128GB SATA III MLC Internal Solid State Drive (SSD)
And a nice fat storage drive:
$140 Western Digital Caviar Black WD1002FAEX 1TB 7200 RPM 64MB Cache SATA 6.0Gb/s 3.5" Internal Hard Drive -Bare Drive
A little over, so adjust to taste. Mobo, processor and ram of course are the most important. This should be a build that will last you quite a while.
SSD's are still at a premium, but they are coming down (should break even at $1=1gb later this year) so if you have an old HD you could temporarily use as an OS drive, that would be good. Same with video, if you already have a gaming card you can use for awhile before upgrading.
Also, on the processor, the 2600K is the overclockable part, and the 2600 is the "fixed" part, so you'll save a couple of dollars if you just get the 2600 if you don't intend to overclock. The difference between the i7 and the i5 is also that the i5 does not have hyperthreading. Hyperthreading does make a difference when transcoding and rendering, but it might be something you can live without. The quadcore i5 parts are still quite nice at their price.
Keep in mind too that Intel just launched their Ivy Bridge chips, which use less power and are a bit more powerful, for the same price. (not sure of the part, think it's like 3930 or something, and I believe it also fits the 1155 socket on the board!) So you might want to look into that.