The EFF have published an interesting item on how to blog anonymously. The post has some good tips and some not so good ones, many are also only relevant if you live in the US which while might be good for a lot of bloggers does not cut it for the rest of us.
Again not being an IR/ER expert I do wonder about these sorts of things, does actively trying to hide your blog when you know the content might get you fired actually makes things worse if you do get caught? I guess it would depend on your local legal environment.
A final thought, it is very hard (if not impossible) to really be anonymous in the internet. So it is easier to just “Be Smart”!