A great alternative to re-tuning your guitar is partial capos. I designed 4 new capos for Kyser called the K-Lever Series of Partial Capos. They are:
Double Drop D
and Open G
While there are trade offs with partial capos, the advantages are fantastic. The chord voicing is outstanding and of course the ease of just putting on a capo and you're in an alternate tuning. Google Trace Bundy and watch some of his videos to see what can be done on the advanced end of the spectrum. On the novice end, you are working with familar chord formations since we didn't change the tuning of the guitar. There is no settling in of the strings to their new tension during the song. My take has always been the less tuning on stage, the more fun that is had on stage for players and audience alike.
You can look on My Page to see pictures of these capos and read more. Also check out Gary Lee Joyner's page, he delves into this subject with great expertise.