Since prices keep getting lower, and features keep improving, I’d wait. (You might even be seeing computers with USB 3.0 by year’s end.)
References :

Well, usually the summer months are best, around July, August – Right now, as a matter of fact. But DO do your homework and your shopping around and compare prices vrs features CAREFULLY! Don’t get sucked into the 60 day TRIAL software version of Office 2007. Make sure whatever you get has the FULL licensed version, ok?

Here are some features you might consider for a computer:

mid-tower case – stay away from slim line and other types that you cannot upgrade.

At least a 650 Watt Power Supply
At Least A dual Core E8500 or a Quad such as a Q9550 processor
Minimum of 4 and better, 6 gigs of RAM
Minimum 500 Gig and preferably 1T hard disk
Samsung or Pioneer DVD writer 22X
A good video card – not on-board or internal video. I would say, at least a Radeon HD4850 or GTX 260
If you are going Dell or HP, they will NOT tell you what motherboard they are putting in there but READ THE SPECIFICATIONS first for the computer.
Make sure you get a FULL COPY of the Operating system. Right now, people are gettting Windows Vista 64 Bit Home Premium with a WIndows 7 UPGRADE guarantee.
Make sure you BUY a back up or recovery CD and put it somewhere where you will NOT loose it!
I love logitech mice and keyboards
I prefer Viewsonic LCD’s

On a "deal" you should be able to get something like this for around $650. Be careful to find out the details before you purchase. Make sure you get your software fully licensed and not just some time limited junk!
References :

Black Friday
References :