I'm not sure where you live, but try seeing if you live near a Microcenter. www.microcenter.com has the i5 750 for $169.
i5 - 750 = $169
http://microcenter.com/search/search_results.phtml?keyword=i5+750&category=
If you don't have a Microcenter nearby, and saving money is important, I recommend using Bing Cashback (www.Bing.com). It's super easy to use. I did with my build, and I'm in line to get about $80 in cash back. You have to wait 60 days for your money, but it's legit, and it's green. Tigerdirect/CircuitCity/CompUSA all qualify for 8.3% cach back with Bing everyday, and every couple of days, one, or all three sites, will jump up to 15%, or even 20% on an odd occasion. I used BCB on my Radeon 5850, and got 8.3% off of $299, for $275, with free shipping. So I saved $25. Did the same with my i5 processor.
Also, Ewiz.com gives you 5% off with Bing. Newegg sometimes nets 1 or 2%. Zipzoomfly.com 2-5%. It adds up, especially with Tigerdirect purchases.
Anyhow, back to the build. Remember, I'm trying to stay with lowest price possible, without picking absolute trash for components. You can get some cheaper components, but these are about as low as I'd go.
ATX:
i5-750 Lynnfield -
$187.50
http://www.ewiz.com/detail.php?p=I5-750&c=cashback&jftid=2:091fed2e-b3d8-47c4-b288-d64948bc3490
ASRock H55DE3 LGA 1156 Intel H55 HDMI ATX Intel Motherboard -
$93
http://www.newegg.com/Product/Product.aspx?Item=N82E16813157185
G.SKILL Ripjaws Series 4GB (2 x 2GB) 240-Pin DDR3 1600 -
$104.99
http://www.newegg.com/Product/Product.aspx?Item=N82E16820231277
HEC Combo case & 600w PSU - $61.98
http://www.newegg.com/Product/ComboDealDetails.aspx?ItemList=Combo.358516
XFX HD-577A-ZNFC Radeon HD 5770 (Juniper XT) -
$160
http://www.newegg.com/Product/Product.aspx?Item=N82E16814150447&cm_re=radeon_hd_5770-_-14-150-447-_-Product
HDD: Seagate 7200.12 500 GB $55
Any DVD drive- $20-25
Total: $685
You could probably save a few bucks with a micro-ATX board, and opting for some components with rebate offers. Also, I'd really try to go a step up from the 5770, to a 5830 or 5850. The 5770 can leave a lot to be desired. Moving to a 5830 would add about $80 or so. I did not include a monitor. Prices change on those everyday, and there are a million places to find deals on them.
Like another poster mentioned, an AMD build might save you some money.