Wow, I used to use ARexx all the time back in the early 90s. I forget more about it than most people ever learned (no really, I think my forgetfulness is into negative numbers now). My best resources at the time were ABACUS books, the AREXX bible, the ARexx Cookbook, and ideas and tips from Bill Bowling (author of MEBBSnet BBS for Amiga

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To auto-start ARexx on boot, just drop the RexxMast program into your startup drawer (or a copy of it if you prefer).
You might want to see if any of those titles I mentioned are available from Amazon.com, BN.com, etc. (lots of used books appear on there frequently)
Some other resources:
Arexx Yahoo GroupARexx Programming Excellent for anyone new to ARexx
Alfie's ARexx pagesBruces ARexx/AWNPipe TutorialHope some of that's helpful to you! :-)