[Steve DeRosa]

• CGDA is traditional tenor guitar/banjo tuning - chord/fingering patterns are identical to mandola, or mandolin a fifth lower (notes are fingered the same as mando but will have different names - you'll need to mentally transpose);
• "Irish" GDAE will require heavier strings (TMK John Pearse makes a dedicated set), as well as a setup and possibly a re-compensated saddle in order to intonate properly;
• "Chicago" DGBE is fairly common - an 11-15-22W-30 set should work for most 23" scale instruments, 12-16-24W-32 for short (20-21") scale;
• Drop-G tenor uke tuning (GCEA low-to-high) is a great alternative if you're going to be using it for ensemble work, lending a sheen and sparkle to the high end - I'd only do this one on a fairly robustly-built instrument, though, keep the strings as light as possible consistent with decent tone (9-12-18W-22W should work on ~23" scale, 10-13-18W-24 on a short-scale) and keep an eye on the top/bridge and neck...

Hope this helps...