I don't use a purse organizer, but I think my purse is pretty organized. My strategy - group 'like' things into portable little packets.
1) I keep a very small wallet with only essentials, like cash, ATM card, driver's license, insurance, vehicle reg., gym card, one Am Ex and one Visa.
2) Then I have a smallish pouch with all the other credit cards, store cards and frequent buyer cards. If the pocketbook I'm using on a particular day is too small, I just omit this fat little package.
3) A make-up pouch with sample sizes (and a full lipstick and masquera) for touch-ups, Shout wipes, nail file.
4) Business card holder.
5) Coin holder.
6) Blackberry.
7) A couple of pens.
Every package has a different color so it's easy to grab the right thing without grubbing around too much. By bunching the little stuff this way, switching from one bag to another is fast and easy. Plus, it keeps the inside of my bags cleaner.