Makers of Rhodes, "an open source framework to rapidly build native apps for all major smartphone operating systems (iPhone, Windows Mobile, RIM, Symbian and Android). These are true native device applications (NOT mobile web apps) which work with synchronized local data and take advantage of device capabilities such as GPS, PIM contacts and camera."
"PhoneGap is an open source development tool for building fast, easy mobile apps with JavaScript." Supports iPhone, Android and Blackberry SDKs.