As anybody who knows me or my journal will know - my pet project is Autodia, a small program (or rather a script and collection of associated modules) that generate UML Class Diagrams (which can also be abused as database diagrams) from pretty much anything (perl, c++, php, torque, dbi, sql, python and java).
It has been going for about 3 years I suppose, and in that time I have released about 20 versions (currently preparing 1.12 for release).
In that time I have received email from users in more than 50 countries - many from eastern europe, and even some from the far east.
I have also received patches and fixes from almost 30 people, thats on top of the many more bug reports I get.
And all this for a small programmers utility.
When I see people dispute the 'many eyes make bugs shallow' idea, I now know, that its often true - even though my project is small I get a huge ammount of help - I probably spend less than an hour a week on average working on it now, yet it continues to progress and improve with a flutter of patches and bug reports every month to my inbox.
of course because my tool is for programmers by programmers, users are more likely to give feedback, but it is a lot more than I expect or anticipated.