If you're willing to put in a little work learning some design principles, that will help you out enormously when it comes to deciding which logo is best for your product. Whether you buy an inexpensive one off the web or create one yourself, you'll be able to make better design decisions.

For an introduction/overview to logo design and a set of resources, check out: http://justcreativedesign.com/2008/12/02/logo-design-resourc... Especially spend some time looking at logo redesign critiques since you'll get a better feel for why a particular logo might be better or worse. Also find some examples of bad logo design - that should give you a sense of what to stay away from.

To learn how to think about logo creation, skim a bunch of the "process" and "logo design roundup" posts: http://imjustcreative.com/category/branding-identity/ If you decide to create your own, a typographic logo is probably a good place to start and there are several of the "process" samples that go into a lot of depth for that type. This is my single favorite place to learn about logo design.

And finally, for a solid overview of graphic design principles, there are a bunch of good tutorials collected here: http://psd.tutsplus.com/articles/web/50-totally-free-lessons... Knowing a few of the design basics will help improve everything you create (not just your logo) much more than you may realize now.