I go through stages...
When I carry a large bag, I add a quilting project to it, a library book, and sometimes my netbook. I also have a bottle of water and snack in my bag, and a blood sugar monitor. If my brother travels with me I carry a large bag because he has to carry Depends everywhere and I can "hide" them.
I have a special large purse I carry on Sundays that will hold my bible when the bag is zipped.
During the regular times, I carry a quilted purse that is medium sized and change it often with the seasons or the mood.
Sometimes I just carry a wrist wallet with my keys and id. I wear it like a corsage. ;-)