Jon linked to concertina.net - they have an "ABC Convert-A-Matic" page that is very easy to use. This thread (click) has some tunes you can use for practice, and I'll post a tune below.
All you do is highlight and copy [CTRL-C] the ABC tune from the Mudcat message, and then go to the converter and paste [CTRL-V] it in and hit "submit."

Here's a tune to try:

X:1
T:Gentle Annie
M:4/4
L:1/8
Q:140
K:D
F> E | D2 D2 E2 D>E| F d3-d2 c B | A3 B D D E F | E4 z2 F>E| D2 D2 E2 D> E| F d3-d2 c>B| A2 G F F E D C| D4 z2 A A B e3 d3 B| A4 F2 c d | F3 E D D E F | E4-E2 F>E| D2 D2 E2 D>E| F d3-d2 c B | A2 G F F E D C | D6|

Copy the entire part that's bold, from X:1 to the last note. The tune is from a questionable source, but it does work.
-Joe Offer-