QUOTE(fsharpminor @ Jul 15 2009, 11:26 AM)

I think there are some by Mozart, but maybe rather easy.
Does that matter? If it's about having fun then something not too challenging to overlay the parts on is a lot more enjoyable.
Look for oboe or flute duets, of which there are plenty.
Amongst the more challenging duets written specifically for violin, are those by Mazas (at least 4 books of them), Pleyel (one or two books - the 2nd violin part being a rearrangement of what was a piano accompaniment so lots of double and triple stops), and Viotti (at least 4 books of these) and Bach (these are actually very difficult to play). Do not be fooled by the words 'Easy' or 'Elementary' in the title of any of these composers violin duets... to do them justice they require at least Grade 6+ in playing standard!
Chappells and Schott Music in London will stock most of them. If you order before 11.30 in the morning from Chappells, your music will be in the post 1st class on the same day.