What class(es) are you running? For 1/10, either the Checkpoint 19T or the Komodo Dragon motors seem to be the most popular at our indoor track. For 1/12, the Komodo is the one to get. As mentioned previously, you can either get either of these motors from your local hobby shop or track or pick one up from one of the many motor tuners out there. Try looking at www.tmxpress.net
(eXpress motorsports) if you want to buy from a tuner. I have had great results with their products.