I have recently made a plugin that uses the Google translation service to translate the page a user is on (download from http://getinternationalclients.com/translation-plugin/).

Making a plugin, widget or toolbar is a great way to make something that can go viral. It can be hard for a lot of people to come up with an idea.

If you have the idea, but not the skill to make a product, you can always find people to write the code for you online. A widget will cost $50 to $100 which can be inexpensive if it get you traffic that converts into buyers.

also, the guys over at 97thfloor.com have some good viral marketing articles, I just today sent two to my clients so they can get an understanding of ideas they could find within almost any business