I gave a brief introduction to PhoneGap and briefly showed how to use it to create an app for Windows Phone 7.
The main place to go for all things PhoneGap is http://www.phonegap.com/ but if you're after the Windows Phone 7 version this is currently at http://github.com/mrlacey/phonegap-wp7. (Please note that the WP7 version on GitHub doesn't work with the RTM tools. I hope to upload the fix for that tonight. Lots more excciting functionality will be coming shortly too.)
If you've built Windows Phone or Windows Store apps you can cross-promote them with AdDuplex to get more users.