I've been arguing with my old White serger (it loves to skip stitches on the left needle), so I decided that it was time for another machine before I send the White to the shop for repairs (or replacement). I managed to find an even older Bernina Bernette MO-335 on Craigslist that had hardly been used (the prior owners were intimidated by it) and jumped on it. Now that I have a reliable serger (the Bernette is this side of an industrial machine), I actually need to learn how to serge something other than a straight line.
There's some really nice books available, but it's nice to find some generic information is still available through the Extension Service:
Serger Basics - Level 1 (Kentucky Extension Service)
Sewing with Serger Basics (Utah Extension Service)
Bernina Workbooks - Even though they're for Bernina sergers, There are techniques that can be used on most machines
Bernina Serger Workbook 2
Mastering Your Bernina
