I'm not one for overly big bags but ones that are medium sized and with a shoulder strap. It's just easier for me to carry my things around.

I got to think about what you carry in your bags during the work week because I see ladies on the subway with 2 huge bags of stuff then their purses or handbags.

Here's my list:
wallet
blackberry (work)
IPhone
makeup bag
keys
extra shoes or sneakers (if heels begin to bother me)
gym clothes (although I take extra clothes to work at the beginning of the week)
bike lock
Kindle or book
gum
lots of loose change (sometimes my bag weighs a ton)