You can probably get it on sale at Microcenter but its going to be a walk in only. Other than that you aren't going to find it much cheaper. The prices are set by Intel and regular prices don't usually drop 20 or 30 dollars. Unless you find a great sale don't expect to get a 220 dollar CPU for 20 or 30 dollars under retail.
Well, it depends on how patient you are. Obviously, Microcenter is your best option if you have access to one. Other than that, I'd suggest signing up for updates on both Tigerdirect and Newegg. They have deals every weekend and sometimes send you 24-48 hour coupon codes.
The typical price for a NEW i5-2500K is $220, but with coupons I got a brand new one for $200 with coupons that Newegg sent to me. Also, there are holiday deals on both sites.