We now have 2 {GS} servers on L4D.
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Versus @ 8.12.65.230:27015
Campaign @ 64.156.14.32:27015
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Neither require a password, so they should both show up in your community server list. Just give it some time to load.

If they don't show, you can start a lobby for the game of your choice, then the lobby leader imput one of these into console:
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Versus : sv_search_key gsclanvs

Campain: sv_search_key gsclancamp
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That SHOULD put you into the {GS} Server.