Here is the latest update:
http://www.fileplanet.com/download.aspx?f=57317
Looks like gamespy has a Australia/New Zeland DL server so it shouldnt take too long.
The official expansions are as follows:
Opposing force: You play a member of the Special Forces team sent in to clean up Black Mesa.
Blue-Shift: You play Barney, one of the security guards.
both are good, both were put out by Gearbox, so they are very consistent. they also overlap with scenes from the original, which is cool.
Counter-Strike is a "relaxed-reality" reality mod with terroristst vs counter terrorists. it is currently and has been for years) the #1 played online multiplayer game ever. it is awsome, i love it.
Day of Defeat is another very popular multiplayer mod, it is based on ww2.
There are also Team Fortress CLassic and FireArms, plus Death0match classic (a quake-themed multiplayer mod for hl)
there are tons and tons more. Natural selection is another big one, as is Sven-coop. most i have played (all of the above at some point) and all are good so far.