This is Free?
There was a time when you had to pay to get you hot little hands on these games. But this is the age of electronic enlightenment and when a game line ends there are sometimes good people out there willing to do the right then and post it as a free PDF version.

The following are links to the home sites of free games. I have not reviewed any of these games because as printed books they have already recieved plenty of attention on the web.

Ars Magica Fourth Edition (Atlas Games) 
Ars Magica represented a seminal turning point in the conceptof the magic system in is heyday, and still manages to make many recent publications look like refugees from 1983.

Harn (Columbia Games)
The more realistic than reality rules set for medieval gaming. Harn is very rules intense, but has its fair share of loyal followers.

Tri-Stat dX (Guardians of Order)
Widely hailed as one of the finest rules-lite systems to come out of the woodwork in the last few years, Tr-Stat dX has been made available for free by the nice folks at Guardians of Order.

Witchcraft (Eden Studios)
From Eden Studios, Witchcraft is a nice little dark, urban fantasy game. Very solid post-White Wolf desgin, and arguably the direct forerunner of more recent Eden Studio sucesses, Witchcraft is definitely worth a look-in.