Loads do mp3 ringtones now:
Almost all new Sony Ericssons (k700 k750 s700 k500 etc)
Samsung D500, D600
The moto v600 onwards should do mp3 ringtones too i think.
Very few nokias do mp3 ringtones. I personally am not a nokia fan, but at the same time do not wish to offend any devout nokia worshipers. Everyone has their own taste.
I have an SE k700 and love it.
BE WARNED!!! The Motorola V3 only has about 4mb of memory to store mp3s on!!!! About 1 or 2 full songs!!!!
Whereas the others have much more:
k700 = 34mb
k750 = 96mb
D500 = 96mb
you get the idea...