JustOneClubCard.com is your solution to a wallet full of discount or membership cards. For that reason, this one is primarily for the guys (or women that use wallets exclusively [as in with out a purse]) where carrying space is at a premium, though it can help woman clear the clutter as well.
The concept is simple enough, transfer the bar codes from the cards onto one card. The bar code tends to be the only important element of the card, but generally takes up less the 1/4 of the surface area of one side of the card. Doing some quick mental math, if you compiled the bar codes onto a single card you could replace eight regular cards with one new one.
JustOneClubCard.com works simply enough. Select store that the card was issued by via a drop down menu, type in your bar code number, repeat as necessary, then print. If the store you need is not offered you can switch to the advanced view at http://www.justoneclubcard.com/index.py?view=advanced. Their you can select what type of bar code it is. The rest of the process is the same.
To help potentially confused staff who you will be giving the special card to, you can print out sleeve which makes only one of the bar codes visible at a time at http://www.justoneclubcard.com/JOCC%20SLEEVE.pdf
I have not used this site myself, but that is because of my general aversion to those discount and membership cards. If my aversion changes or I find myself forced to get these cards, it is likely that I will use the site to clear the clutter.