MADDE - Very usable multi-platform cross-compiler. It is a command line utility that can compile, build, and it can also make .deb packages.
Nokia Qt SDK - Multi platform development tool for both Symbian and Maemo. For Maemo, it uses MADDE under the hood. It has a nice IDE (Qt Creator), and is easy to use.
(It has some minor flaws that will be corrected in the next version.)
