Mascagni Intermezzo
I love arranging because of one word: empowerment. Through arranging, thousands of works are now possible for your group to play. With a few simple tools (basic knowledge of music theory and orchestration), and some spare time (not always so easy to find), you can take something and make it yours. The Intermezzo was one of the first arrangements I did for Palaver Strings (the group featured on the recording), an awesome Boston-based chamber orchestra. One of the guiding values of this arrangement is equality - everyone in the group plays the melody and gets an equally fun part :)
One more thought: Having the right tools is central. If you're serious about arranging or composing, I would highly recommend investing in some good software. The time and headache you save is tremendous. I use Finale, but I have no qualms with Sibelius either.