Hi! If you are interested in a high-end solution you could test Cosa. It supports ATtiny (X4, X5, X61), Standard (Uno/Mini Pro/Nano/LilyPad) ATmega328P, Mighty ATmega1248 and Mega ATmega2560. The platform contains 50+ classes, 25+ device drivers, low-power and object-oriented event driven programming. All integrated and ready "out-of-the-box". Code can more or less be moved between the different targets by simply selecting the target board. https://github.com/mikaelpatel/Cosa
Follow the link to the blog and on-line documentation.