Cutting boards: What are some general tips on purchasing and using a cutting board?
Besides the material itself, there are lots of other factors -- 

Surface : There are smooth plastic cutting boards, and there are rougher ones.  I prefer the rougher ones, as smooth means things are slipping all over the place and its can be dangerous.  Plastic will roughen up with use, but cuts and nicks in plastic boards means more places for germs.  For those thin plastic cutting mats, they're so lightweight that you have to worry about both the food sliding, and the mat itself sliding.

Thickness : Those 'butcher block' wooden boards look great, but I don't like them for two reasons: I'm short, and it raises the surface that I'm cutting at; they're heavier, and I like being able to pick up my cutting board to take to my stove, as my cutting area is near my sink, not my stove.

Size : Large enough to hold the amount of food you tend to prep at one time, and not so overly large that it's a pain to move / clean / etc.  I like about 18" x 24" (45cm x 60cm), but if you're cooking for one in a small apartment, that might be a little large.  (although, one of my apartments was small enough that I used a large board, so I could span the sink, as there was all of maybe 30" (75cm) of counter space.

All this being said -- I use wood for all vegetables, and plastic cutting mats for meats and poultry, just because it saves me time sanitizing everything between cutting.  (although, I typically try to cut all of the vegetables first, then the meat, just to save on cleaning a knife).

Part of the complaint against wood is that it's very hard to get germs out once they get into wood -- but research has shown that if you clean the surface, wood cutting boards are unlikely to transfer germs to other food, and a well-maintained wooden cutting board will self-heal and continues to be safe over time, whereas plastic can't be simply wiped down once it starts developed scratches from use.  To sanitize wood boards, use half a lemon, and coarse salt (I use kosher salt), and use the cut side to scrub the board.  Rinse, let it dry, and give it some food-grade mineral oil every few months, depending on how humid your area is.  If it's looking sad, you can always sand it down, re-sanitize it and re-oil it.