By the way I wasn't kidding about its potential.

For GPS you can buy or download GPS software for WinMo platform, there's many. You can easily obtain pirate copies but I'd have to advise against it. "Route 66" is a freeware (afaik) and its better than Google Maps (iPhone) but not as full-featured like the big brand names (TomTom etc.). You can also load Android into the device (if you dont want to use WinMo) and use its Google Maps software from that.

After loading XDAndroid 2.0 ROM by xda-devs you can access the Apps and emulators for Android.
Just make sure to save your original OS, flash to a LITE WinMo that automatically loads Android for you by Haret.
Haret loads other OS's (eg Android) and totally kills all WinMo running tasks, so that Android OS is running natively and not emulated. Its not as convenient as dual-booting or full install into the NAND (ie the phone) but it is far better than an emulation.
Also make sure the copy of Android includes a "custom made" 3D graphics driver which couple dev's built from scratch (since QLCM drivers are licensed)

All emulators should work and at full speed (otherwise at decent speed) without overclocking, with sound and no frameskip ....except DOSBOX, N64, Dreamcast and upwards (which is too slow/just unplayable).

So once optimized these ports give you a vast repertoire of titles; which is reflective of N900's possibilities -less N64 emulation.

If you don't like Android or don't wanna mess with the flash NAND you can use emulators built for WinMo.

Like here is the PSX emulator and SNES emulator for WinMo.