I'd recommend the Parkzone Slo-V as a terrific beginner's electric Ready-to-Fly (RTF) RC plane:

http://www.parkzone.com/Products/Def...ProdID=PKZ1300

It flies slowly enough that it can be flown in a typical gymnasium, but can also fly outdoors with low wind conditions. With an almost four foot wingspan, it's larger and more stable than most other RTF airplanes in its price range. Because it's from Parkzone, most any hobby store will be able to supply any spare parts (most commonly props, wings, tail assemblies) as needed.

The Slo-V is a great place to start if you don't want to spend the extra $50 or so to jump up to the Hobbyzone Super Cub or the SkySeeker GT from http://www.readytoflyfun.com for example.

There are a lot of good electric planes for the beginner in the $150 to $250 price range. If you really want to spend no more than $100, the Parkzone Slo-V is one of your best options.