It is a proper subject, may be better suited to the business forum though...
If you are looking at consignment, make sure you are aware of the % they will take. They will display and sell it, for a price. If you are dealing with people you already know, they may just do it for the warm fuzzies they get from helping someone.
If you are already selling books and cd's, throwing some photos into the mix is no big deal. But make sure if you are deducting the cost of printing and framing, you are claiming the income. Photography is one of those things that the IRS pays special attention to.
It's not much different than a music gig, with the exception that you are leaving someone with a print you may have payed quite a bit of money to frame (I just sold two big wall portraits, framing along cost close to $400) who really has no vested interest in the product. If it gets damaged, no big deal to them, bigger deal to you, who has to eat the cost to repair.
Also, be aware of the fact that working with friends doesn't always go so great. Minor hiccups can be blown into friendship ending disasters.