[OT]
Well, actually there is usually a bijective map between the two, assembler being the human friendlier version of ML.
The greatest downside of assembler is, that there's a unique language for each instruction set. The principles don't change very much (but remember: ARM is a RISC architecture), but to learn the priciples (pointer etc.) you don't need the language (as said before).

[/OT]

@panjgoori: I agree that Python is a good choice, it even has bindings to Gtk and Qt. However starting with Qt and C++ is also possible since Qt only needs a tiny portion of the features of C and C++ on your side (it uses more of them internally). Another advantage is, that you don't need to install scratchbox. Qt SDK comes with a tool called "mad" that alows you to use the same comands for building the software for normal Linux and Maemo (e.g. "dpkg-buildpackage" becomes "mad dpkg-buildpackage").