Though they can be reused in a number of ways -- to line small wastebaskets, for example -- bags from supermarkets have a way of piling up in an unwieldy mass.
One solution is to store them in large empty tissue boxes, folding them neatly ahead of time; when you need a bag, simply pull one out. You can also buy inexpensive organizers for bags; many plastic versions are similar to a large tissue box -- a good choice if you have space under the sink. Also available are long cloth tubes that are cinched at the bottom and can be hung for easy dispensing -- this option is helpful if you have space on a kitchen wall or inside the pantry to place the tube.
Although these ideas will keep plastic bags tidy, the best way to deal with an overabundance is to avoid bringing home so many in the first place. Consider buying several large, inexpensive fabric totes, and keep them in the trunk of your car so you can use them instead for groceries. Or keep the bags to a minimum by recycling them from time to time. Many supermarkets have in-store bins to collect your unwanted bags.