Can you read music?

Do you have (or are willing to buy) MIDI software? If so, check out the beautiful arrangements here:

http://www.contemplator.com/folk.html

Other ideas:

One simple idea for arranging is to use a Question and Answer format. Let one player play one phrase (which seems to be a question) and let another play the next, which seems to be the answer.

For variety, figure out a one-note drone which goes with all or part of a piece. Fiddle could play it steadily; others could pluck it. This is good for pieces which go up and down the scale a lot.

Figure out harmonies in "thirds" for part of a piece. (not every note is actually a third - harmonize with the chords being used.)

Use variety in accompaniments. So many guitarists just strum "blang blangety blang." Add fingerpicking and bass runs - vary your playing. Also, move up and down the fingerboard. For example, there are low G chords and high G chords.

Here's a tip I got from choir director. If you have a 4-part piece, take the tenor line, raise it an octave or two and turn it into a descant. (probably the fiddle would play it) Fancy it up a bit with little runs and dotted timings.

I hope you have fun. My band does this stuff all the time.