You might try this "web" thingy. Rumor has it that people from all over the world use it :)
Seriously, put up a small site on a cheap hosting service that details what your library is, why it exists, why it is superior to other similar libraries and make your library a download from there. Maybe throw in some code samples showing how to use it.
The key is to make it searchable so that it has a chance to appear in search results when people are out there looking for solutions to the problem you are solving. Make sure people know it is beta and that they have some way of reaching you if/when issues come up.
Even better, if this is an open-source project, you might be able to put it in Codeplex, which handles a lot of these things for you.
You also might want to promote it in an ethical manner. By that, I mean search out discussion boards where people are talking about the problem your library solves and for just the people affected, post a message that your beta library might do the trick for them and include a link to your library site. You must be responding to valid related messages, otherwise the moderators will (rightly) consider you a spammer and kick you from the board.