Here are interesting links to start to work on OSGI :

1) Neil Bartlett : http://neilbartlett.name/blog/osgi-articles/
2) Osgi for beginners (Serverside): http://www.theserverside.com/tt/articles/article.tss?l=OSGiforBeginners
3) JavaWorld :
- Part1 : http://www.javaworld.com/javaworld/jw-03-2008/jw-03-osgi1.html
- Part2 : http://www.javaworld.com/javaworld/jw-04-2008/jw-04-osgi2.html
- Part3 : http://www.javaworld.com/javaworld/jw-06-2008/jw-06-osgi3.html
4) Spring Dynamics Module : http://www.springframework.org/osgi/demos
5) Apache Felix : http://felix.apache.org/site/tutorials-examples-and-presentations.html