I have been looking to flashes lately, and according to many reviews, the Canon Speedlite 580EX is the very best Canon flash you can get. After spending hours and hours on eBay, I found a seller with a Canon Speedlite 580EX in mint condition, available at a good price. Seller has perfect 2000+ rating too!

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=220474825860