I'm sure there are websites that list a lot of common services and provide some advice on which to get rid of, but why search elsewhere to find them? Query for things like "service rid" or "remove services" and that pops up some useful posts - people are always trying to get rid of uneeded services. You can also check out http://www.linuxquestions.org/questi...=rid+services.
That is one of my old posts.
I won't tell you that you can go ahead and eliminate portmapper. I will say that you probably don't need it. The best way to know is to just eliminate the service and do what you normally do on your computer, noting what things do not work (if any).
I run all sorts of stuff without portmapper running at all. In the end though, only you can make that decision - do some research on what exactly it does (I know its basic function is to let outside connections know which port to connect to on your computer) and then you can feel free to cancel out its /etc/rc.d/<script> entry by renaming it (mv <oldname> <newname.old>).
Let me know if that clarifies.