Not a site per say but a big piece of infrastructure. Before there was Steam there was Sierra's website which hosted half life updates, and World Opponent Network, a matchmaking service from Sierra who eventually got acquired by Valve. You would access WON through the half life game. Using it for online play was downright hilarious, especially because everyone was playing on dedicated servers with manual patching. A new version of the HL server / client would drop on Sierra and you would have to get in line and wait for hours at File Planet or Major Geeks or another mirror in order to download it. For like two weeks you would be getting version conflict errors because 50% of servers / clients would patch quickly and the other 50% wouldn't. Searching for a server was pretty much like using grep, there was no friends list or chat, it was amazing hahaha.