Originally Posted by TOG Unknown
To find the link to your Steam community page:
fire-up the Steam client;
within Steam are a number of tabs (Store, Community, My games, My media, Tools) - click on the "Community" tab; and,
when the "Control Panel" page fully appears, just below the tabs will be a Web browser-style bar including an address for your Steam community page (eg., http://steamcommunity.com/profiles/<some-number-here>/home).
A Steam update removes the url display by default. If you don't see this go to
Steam > Settings > Interface > Tick the "Display Steam URL address bar when available"
You should be able to highlight that address then right click to select "Copy" so you can paste it somewhere else (in a post here in this thread, in a PM, etc.).
There are a number of TOG-related Steam groups for various different games, including (but not limited to) Team Fortress 2, Left 4 Dead, Day of Defeat: Source, Counter-Strike: Source, Trackmania United Forever, Call of Duty: World at War, Killing Floor, Rainbow 6, Insurgency, etc.
Some of these groups are tied to a TOG division (eg., Team Fortress 2) so to get an invite, you just introduce yourself in that TOG division's forum; for others that are just loose collections of players for a potentially less popular game, contact one of the listed admins for that group to get an invite (assuming it's not an open/public group, in which case you can just join it directly).
In the first case, you'll probably be sent an invite to the general TOG-wide Steam group - you can sort out what additional groups you want to join from there.