PhoneGap is an HTML5 app platform that allows you to author native applications with web technologies and get access to APIs and app stores. It is open source and supports many native features over 7 mobile platforms.
After trying many featured apps built using PhoneGap, I see that apps quality are quite good but some times screen flickering happens (which gives you the feel what you are using a browser).
Some stackoverflow posts shows that these flickers can be solved but I did not give it a try.