If you like last.fm, but (like me) you don’t like all these shiny gui players, because you think that you don’t need a gui to play music, you should try out Shell.FM. Shell.FM is a very simple console player for last.fm, which seems to have all the features of gui players. The interface is not very intuitive, but it’s well documented and quick to learn. Anyway, you just need to enter your username and password and it will start playing your favourite songs. It is written for Linux, but will probably run on any unix-based operating system. For now it ran very stable on my ubuntu-based multimedia-system.
You can find everything you need at http://nex.scrapping.cc/shell-fm/
If you like this program you should also consider joining the group shell-fm on last.fm, where you can find some more stuff, like a perl module to control Shell.FM over a socket, an LCD module to output the status through lcdproc or a port to ARM which will make it run on some handhelds.