I like to change my purse with the seasons, using a more compact and colorful one in the summer and a slightly larger and darker colored one in the winter. Whether or not you change the actual purse, this is a good time to take a look at what's in yours and get it organized for the coming season.
This is a great 5-10 minute organizing project.
P.S. If you often lose your keys in the depths of your purse, use a carabiner to clip your keys to the strap and you'll never have to search for them.