RTW tickets aren't generally available or bookable on the 'net. Some private smaller travel agents often show prices on their homepages but they are often outdated. An agent I've used is Around the World Travel in Seattle located at (regularly updated):

www.netfare.net

(Please don't take offense at my next comment) They are an excellent (and busy) agency so if you aren't serious please don't waste their time.

As for ff miles - Delta seems to be the best - around 150,000 Skymiles - however I might be wrong.