You can sell WordPress plugins as long as:
1. There is a real need for the plugin and it does something very useful.
2. There isn't any competition with a free plugin.
3. The plugin is reasonably priced, such as $20 or $30 for a multi-site license. If the plugin helps to generate revenue (such as phpBay Pro or a shopping cart) you can charge much more.
It can be hard to find a plugin solution that fulfills all three.
I also like jakki's ideas, although I suspect that donations are not easy to extract from most web users.
Last edited by TopDogger; 4 April, 2010 at 23:26 PM.
"Democracy is two wolves and a lamb voting on what to have for lunch. Liberty is a well-armed lamb contesting the vote." -- Benjamin Franklin