About a year or so ago I realized that all of my prints were in a very odd aspect ratio, and if I bought one, there would be no store that would have an affordable-ready-to-buy-off-the-shelf frame that it would fit in. I could get stuff custom framed but that is pretty damn expensive.
So I did some research (mainly at Michaels craft store and Aaron Brothers frame store) and I found a list of sizes that pretty much every store carries in almost every style. Some brands do make frames in the weirder aspect ratios but its safer to go with the most common sizes to assure that whoever buys your prints is going to be able to walk into a store once and be able to walk out with a frame that will fit the print.
Here are the most common sizes I came up with (also standard photo sizes):
While this is a hassle because some of these sizes do not share the same aspect ratios and you have to kinda crop and tweak your work to make them fit, in the end you are making it easier for your customer to better enjoy the print by not making them go out and hunt down some off-kilter frame size.
Hopefully a few people will find this information helpful.