I never turn off my GPS and notice no particular battery drain from it. GPS is a receiver, not a transmitter, and outside of an occasional app using it for updates (like weather), which you can control the fequency of, it stays off. Every once in a while, I may notice my GPS icon on and if it doesn't go off in a bit, I reboot the device. That might happen once in a month. If you are noticing yours on more often, then you likely have installed some poorly written app that is not cleaning itself up after its use.
There is a free app called widgetsoid that lets you set up short cuts (i.e. setting up a GPS toggle) that show up in your notifications pull down. However, I believe that if you're toggling GPS off/on when needed, it often takes longer to get a GPS lock, which can be frustrating if you want to get a quick look at nearby stores in Places, or want to hit the mic button and say "Navigate to ..."