>Unfortunately, this means that what potential employers are seeing is stuff that I've done in my almost non-existent free time, so it's generally unfinished, unpolished projects that had a really simple goal or were for learning a new language/framework. So, it's not necessarily a good indicator of what I produce when I can focus full time on a project.
That is a tricky situation to deal with. On the one hand, you don't want them to think that this is you at your A-game. On the other hand, the naive approach of apologizing in advance is just bad psychology. I don't have experience with presenting this to employers, but in general the best way to frame those kinds of things is to think not in terms of expectations (you actually want expectation high; people see what they expect), but in terms of objective context.
If you say "Here's something I did which really isn't me at my best, but it's what I had time for", then people will expect crap, and that's what they'll see. If you say "This is something I built in my free time", or "This is something I built while I was learning Backbone" (and keep you tone enthusiastic, not apologetic), then people will understand the context in which they should be judging what they see. If they're smart, they'll realize that seeing what you can do when you don't have much time, or when you're on unfamiliar ground, is at least as valuable as seeing what you can do under ideal conditions. If they're not smart, do you want to work for them?
>I've even tried a few times to get tools I've created released as open source, but the general response I get is, "uh, why?" I can understand that the companies see no value in it and in fact may cost them money if there end up being licensing or other legal issues.
That's hard too. It might help if you can come armed with some benefits of releasing something as open source, like the fact that other people will be able to find and fix bugs for your employer, which is basically free labor.