has been mentioned above, and that is a great resource. The only drawback is that there is a file size limit of 100 MB, but since that is quite a large file size for the average length pop/rock song, it is unlikely that you will hit the limit there (I have only hit that limit once, when I was converting a video to an mp3).
Do bear in mind, however, that Zamzar does not let you have fine control over the quality of the conversion.
If you want that kind of control, then I suggest that you download CDex (also free), which is a program for ripping CD's to either .WAV's or .MP3's. Even though it might look a bit daunting at first, once you get to understand the various options for .MP3 quality (and there are a lot of choices), it is very quick, easy and convenient to use. I must admit that it took me a couple of days of reading to understand things, but I was able to then pass on that knowledge to my Dad in 10 minutes.
It looks like there are various people putting out this program (it is an open-source code, I think), but I think that this version is the closest to what I havehttp://cdexos.sourceforge.net/?q=download
Exact Audio Copy (EAC) is another CD ripping/conversion program, but is more complicated than CDex, so I would stick with CDex.