I like to have about a tablespoon of flax seed (freshly ground) on my oatmeal. I buy something called "golden flax" (Now foods has it for a good price), which is a nuttier tasting flax than the regular brown stuff. I just picked up some flax oil on sale to try it. It's pretty wretched by itself (kind of motor oil tasting, though I don't know how I know what motor oil would taste like!), but the icky taste (IMO) disappears somewhat when you add maple syrup to the mix!
Flax is high in omega 3's, while many other oily foods Americans eat are high in omega 6's (like "wesson" type oils, corn oil, etc.). Omega 3's act somewhat like antioxidants, while too many omega 6's act like oxidants. It's a good idea to make sure to get good sources of omega 3 in the diet (like flax, canola oil, olive oil, some fish) to help correct an imbalance of 3s vs 6s (it's best to have a balance of around 4-6:1 omega 6's to 3's, but many people eat closer to 16:1 (exact ratios may be off a bit, as I'm going from memory).