I know it really depends on what you want to test, but personally I prefer to divide speed tests to raw media speed and file system performance. For raw media speed read/write speed I use dd to read/write the media directly (e.g. dd if=random.static of=/dev/foo bs=1M). For file system performance, I've found bonnie++ to be sufficient. If you want to compile bonnie++ as a Debian package, just grab the sources from unstable; it should compile nicely for Maemo (at least for Diablo) as well.