JTwitter is a robust, easy to use library for working with Twitter. See http://www.winterwell.com/software/jtwitter.php for info.
Developed and maintained by Daniel Winterstein of SoDash (http://sodash.com). Released under the LGPL license.
Open source notes: You must let your users know that you are using the JTwitter library, which they can get the source code for. A credit on your home page with a link-back to our page, e.g. "built using JTwitter", is a good way way to do this. Your own code can be licensed commercially however you like and you do not have to release the source code.
The Android classes require android.jar to compile.
If you have a real adt install, then you should reference it's copy of android.jar
Otherwise, a small dummy Android jar is provided in the liblocal folder. If you copy android-dummy.jar to android.jar, then AndroidTwitterLogin will compile.
This jar has some class stubs -- enough to keep Eclipse happy. It does not contain any real working code! It should not be shipped as part of a production system.