Commuting - A really small bag..

Sorry if I am bit off kilter here. I am looking towards commuting and I have a road bike... I dont want to attach panniers because I will never need all of that space... I dont want to use my Jansport backpack primarily for sweat and size reasons... In short is there a bag I can somehow attach to the triangle of my bike or someplace else, which is small, space enough for a shirt and a wallet+cellphone, without having to take a backpack or panniers.. I would be open to a very small backpack too... I tried search but didnt turn up much.
Thanks,
-AJ...

Get a rear rack and a top bag for it. it's what I use and works fine for limited volumes.

Here are a couple of options:

http://www.rei.com/product/10402642.htm

http://www.rei.com/category/4500851.htm?vcat=REI_SSHP_CYCLING_TOC

You could get a largish handlebar bag and some Carradice-style underseat bags may do the trick as well, but I think a frame bag may be just the thing for you.

http://www.nashbar.com/profile_moreimages.cfm?category=66&subcategory=1006&sku=6799&brand=

Ya, i would go for the larger underseat bag. They are usually pretty easy to remove.

How about a BIG saddlebag? It should be big enough for your shirt also....

A carradice SQR saddlebag with a quick-release mount would be ideal. They have much better volume/weight ratios than a rack+rack-top bag.
http://www.carradice.co.uk/sqr-products.htm

Thanks for the opinions all... I am really liking the carradaice saddlebags/big seatbag.. The frame bag looks like a good fit too.. Something detachable is great between rides and commuting... I will post later as to what I end up getting...
-AJ...