I'm half-tempted to write my own, but I don't really have enough time right now. I've seen the Wikipedia list of open source crawlers but I'd prefer something written in Python. I realize that I could probably just use one of the tools on the Wikipedia page and wrap it in Python. I might end up doing that - if anyone has any advice about any of those tools, I'm open to hearing about them. I've used Heritrix via its web interface and I found it to be quite cumbersome. I definitely won't be using a browser API for my upcoming project.
Thanks in advance. Also, this is my first SO question!
I've used Ruya and found it pretty good.
Another simple spider Uses BeautifulSoup and urllib2. Nothing too sophisticated, just reads all a href's builds a list and goes though it.