I haven't modded anything for a long time so I don't recall all the mods I've had in the past.  I do remember having several for BF2 and Morrowind though, and up until a couple months ago I had the Zombie Panic mod for HL2.

The only mod I still have installed is one called "Revolt" for Call of Duty (the original for PC).  It's a modern total conversion.
Unfortunately, there are rarely any servers up for it anymore, but at one time it was really active.  I still play it in LANs though.

To answer your second question, I don't really have specific mods that interest me.  If I mod anything, it's usually by word of mouth or whatever is rated highest on mod sites.
Also, if it has zombies, that is a plus.

I don't play PC games anymore. Hardware is too expensive for me to keep up with. That being said, the last game I played with mods was Unreal Tournament 3 on my PS3. The last game I played with mods on PC was probably the Quake 3 conversion turned Dragonball Z, Bid for Power.