Here are some nice pages explaining how to create stripes (horizontally) in knitting. Knitty has a nice article in the "Techniques with Theresa" section explaining how to weave in ends on garter stitch.
http://www.classiceliteyarns.com/Web...es/Stripes.php
http://www.knitsimplemag.com/node/70
http://www.diynetwork.com/diy/na_kni...357739,00.html
http://www.knitty.com/ISSUEfall04/FEATfall04TT.html
If you are knitting in the round, here is a nice instructional blog explaining how to do striping that I have found helpful.
http://techknitting.blogspot.com/200...s-stripes.html
Katrina