Check out this chart of 2-stroke model airplane engines, comparing displacement, power/weight and much more.
One of the best sources of information is your local hobby store — see a partial list of local stores on the right of this page. Also, you’ll find many good magazines dedicated to the hobby, including specialties such as park flyers, gliders, scale models and more.
There are also a number of R/C-related sites on the Internet. This list contains links to some of the best, including PCC member sites. Explore these links to find many more. Good luck, and happy flying!