GOG Edition:

magnet:?xt=urn:btih:05ED44685201C9C2E217E2F0FC0A53E8F3654C8F  Shadow of Chernobyl
magnet:?xt=urn:btih:CC6F415283BF365842E071D3CC2E403431D93171  Clear Sky
magnet:?xt=urn:btih:F75CE146DB84A3B2B6074BC41615BDD7ECC787F9  Call of Pripyat

.torrent files in the backup repository.
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http://tpb.torrenticity.com/torrent/6758660/  Shadow of Chernobyl
http://tpb.torrenticity.com/torrent/4402161/  Clear Sky
http://tpb.torrenticity.com/torrent/5340194/  Call of Pripyat

If that particular TPB proxy is down, just copy the "/torrent/xxxxxxx/" part to the end of whichever one is up or one you use or even TPB actual site if it's not blocked in your country

ShoC patches:
http://www.gamershell.com/download_18438.shtml
http://www.gamershell.com/download_19083.shtml
http://www.gamershell.com/download_20723.shtml
http://www.gamershell.com/download_21946.shtml
http://www.gamershell.com/download_23660.shtml

install order:

10001
10003
10004
10005
10006

Clear Sky patches:
http://www.gamershell.com/download_32044.shtml
http://www.gamershell.com/download_32532.shtml
http://www.gamershell.com/download_33538.shtml
http://www.gamershell.com/download_35052.shtml
http://www.gamershell.com/download_35296.shtml
http://www.gamershell.com/download_37734.shtml
http://www.gamershell.com/download_44312.shtml
http://www.gamershell.com/download_48240.shtml

install in order you downloaded them (1.5.03-1.5.10), recommend saving them in folder of their own and naming each download 1.5.xx

Call of Pripyat:
No patches, only the Russian version had 2 patches and German had 1 patch.


NoCD
ShoC: http://www.gamecopyworld.com/games/pc_stalker_shadow_of_chernobyl.shtml
pick one appropriate for your version and with a [MULTI4] in name

Clear Sky:
http://www.gamecopyworld.com/games/pc_stalker_clear_sky.shtml
pick one appropriate for your version and with [EFIGS] in name

Call of Pripyat:
1.6.02 either MULTI3 or MULTI5, I personally wouldn't recommend fixed image because you have to manually mount it every time you play.

Mods:
http://www.moddb.com/games/stalker/mods
http://www.moddb.com/games/stalker-clear-sky/mods
http://www.moddb.com/games/stalker-call-of-pripyat

be sure to always check the S.T.A.L.K.E.R. general threads for any developments, recommended mods and general STALKER banter:

http://boards.4chan.org/vg/catalog#s=s.t.a.l.k.e.r.

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Latest edit:
Added the GOG edition torrent links. These are only for /sg/. Please seed. - REPOmAN2v2