One of the many things that I never did before was actually customizing the phone. Neither of the songs that I really liked for ringtone (and were unique enough) were available of course. I found this website: http://audiko.net/en.html that allows to take an MP3 (one that you legally own, of course) and convert it to ringtone.
Here is how it works:
1) Find a suitable MP3
2) Go to above website, upload MP3
3) In editor, select the start and end sequence of the melody - you can listen to it before you finalize
4) Press 'Create Ringtone' and download it
5) Import to iTunes
Could not be simpler than that.
Disclaimer: Uploading MP3 (or even creating them by ripping the CD's) may be illegal in the country you live. I do not recommend or suggest you should do it - I am merely describing a technical process of data transformation and take absolutely no responsibility for any troubles or issues related to that you may get yourself into.