Converting existing tunes in Itunes to mp3

[surrey100]

I have an ipod and use itunes but find the quality if sound on the ipod not that good. I was told by a shopkeeper to convert my music selection in itunes to mp3 as the sound quality would be better but can't find a way to do this. I know how to import a cd to mp3 but don't know how to change tracks already imported into itunes. could find anything on google. any help would be appreciated. Thanks.

[Zylstra]

This online web application doesn't convert multiple files, but it can do it one by one. (And, its FREE!)
http://media-convert.com/

[M1CH431]

This online web application doesn't convert multiple files, but it can do it one by one. (And, its FREE!)
http://media-convert.com/

Thanks for posting that link im trying it out now 

[Mac-G5]

Amadues is your friend!