I was told about this site and their flights seem to be a little cheaper than Orbitz and others. Check them out or let me know what type of experiences you have had with them. www.vayama.com They seem legitimate.
I stumbled on them when I was searching airfares a few weeks ago. Kayak.com searches that website, so I would think it is fairly legitimate.
I found that the prices I found on kayak, orbitz, etc. I could also easily find on the airline websites too.
Just purchased Seattle-Rome tickets from them last night. Obviously a bit early to know, but they appear perfectly legit and other people have used them successfully before. I have received a confirmation from them, and am waiting (up to 48 hours) for them to bill my credit card, after which they will send the e-tickets.
As a side note, I found their website extremely easy to navigate/use.