Here’s a new free tutorial that has been released in the past few days I though was really good to help get you use to rigging up a simple IK leg system, using joints, constraints, nulls and cubes. I though it was well presented and I look forward to seeing more from Psionic’s channel on the subject 
http://www.youtube.com/user/3DGameResources#p/a/u/0/F843jISl7Bc
Also, some of you might not know this but if you want even more on character rigging with free video’s you can check out this section on my blog. There are 40 video’s covering a wide selection of cinema 4D’s character tools, all free and well presented in addition to the bucket full of online tutorials including the use of Motion clips in my section on 3D buzz.
http://www.3dbuzz.com/vbforum/entry.php?2596-Complete-Comprehensive-Cinema-4D-Video-Tutorial-Section
For the 40 mentioned, there is a direct link to NateMac00’s channel here for you to enjoy and for ease of viewing.
http://www.youtube.com/user/NateMac00#p/c/0F9E6B3AEC4D554F/2/X2hz7vW1SSQ