I used to use my dremel to cut arrows all the time. Just like the other guys said cut your arrows a hair long and then sand the ends down to make sure they're square. Or go to Harbor Freight and buy that $20 mini cut-off saw, that thing works like a charm.

http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=42307

Looks like the price went up on it, I got mine for $20 on sale.