If you are stuck for ideas, or just general know how check out these sites:

http://www.vlatitude.com/tutorials.php?tutID=9

http://www.vlatitude.com/tutorials.php?tutID=10

http://www.vlatitude.com/tutorials.php?tutID=15

http://www.vlatitude.com/tutorials.php?tutID=32

http://www.karljones.com/halflife/almanac.asp

http://collective.valve-erc.com/index.php?doc=1047433496-46754900

http://collective.valve-erc.com/index.php?doc=1046839948-87698400

http://collective.valve-erc.com/index.php?doc=1045177834-81552500