An EPP foamie is a good place to start, or if you want a balsa plane people recommend the 3DHobbyShop 41/48" Edge 540 or the 47" Extra 300 SHP. I've also heard it said that the Extreme Flight 48" Edge 540T EXP is great for learning 3D.
When I wanted a larger 3D plane I went with the Hobbyking Galaxy. It's a 32" span, really nice docile slow flyer, very predictable, much easier to fly than my micro 4Site. It's not as durable as the EPP planes but it's a pretty quick build and it's so light and slow that it's very easy to fly. I highly recommend it. It's not that crash resistant but it's fairly easy to repair and I don't crash it nearly as much as the heavier faster planes because it just flies so nicely.
This is my buddies company TAS Foamies. He's 18 years old and just a whizz at flying and designing. He started his own company and I am super proud of him. His EPP Extra is just amazing! Flies light and durable as well! 3D Monster! I will post a link to his maiden on a 30 degree evening! http://tasfoamies.webs.com/3034indoorfoamies.htm