Totally frivolous but here goes.  To start off with, I am very particular about the bag that I sling around my neck on a daily basis.  I try to keep it relatively small and compact to prevent myself from carrying too much but you know how that goes.  I used to carry around a small messenger-style, Tumi bag with a magnetic clasp that I still have but now I am toting a stylish, new Baggalini bag which has more compartments than I know what to do with.  In fact, I confess to walking around for a week before I knew it had a 2nd layer underneath that was hidden by a deftly concealed magnetic clasp.  Yes....sometimes I can be that dumb.  I got it at the www.ContainerStore.com and my mother was so taken with it that she went out and bought the very same bag.
 
Anyway, back to the contents therein:  In terms of tech I carry a Palm Centro (which I love but will gladly give up when the Palm Pre surfaces); a 32GB iPod Touch with Vibe Moda earbuds stuffed with music, videos & apps oh, my; 2GB & 8GB Titanium Cruzer USB drives; a Flip Mino HD camcorder (a new acquisition for stupid fun, mostly it contains videos of my cat and a dog that I babysit chasing each other but I'm sure I will find a serious, business use for it in the future); reading glasses (I am of that myopic age); various rollerball pens (I cannot write with ballpoints -- RSI injuries); earplugs (you never know when you're going to be at a loud concert); anti-bacterial wipes & pocket Kleenex (cause it's yucky out there); other feminine necessities; business cards; credit cards; id cards; Metro card; license; store coupon cards (I wish they'd all get together and come up with one card, now there's an idea).
 
I used to carry (and wonder what I did with it) a small, compact tape measure.  I had one for years that I got as a giveaway at Fund Raising Day in New York and then I replaced it with one from Restoration Hardware and then I guess I lost both of them.  Very useful though in more situations than you can imagine.  I also used to carry a micra-leatherman but stopped after 911 -- something about always having to remember to take it off my keychain in various situations but I should really start carrying one of those again.  Very useful tool. You never know when you're going to need a philips screwdriver or a bottle opener.
 
Anyway, that's what I lug around on a daily basis.  What's in your bag?