I installed ProFTPd on my Ubuntu linux system at home and made my music collection available to authorised users (me). 

A free app, AndFTP, on my HTC Magic works perfectly for logging in and downloading songs to my /sdcard/Music folder....and I can then play them immediately. 

Now my phone can access my music collection from anywhere where there is Internet, via wifi or 3G. 

My iPod Touch can't do it as it needs iTunes to get anything on or off it.