I want one of these, but cheaper.
http://store.apple.com/us/product/MD...n-adapter-02-m
Some options. I don't know what you hope to accomplish so here's a variety:
http://www.amazon.com/iSmooth-iPhone...ning+to+30-pin
http://www.amazon.com/Dragonpad-Ligh...ning+to+30-pin
http://www.amazon.com/ATAirtight-iPh...ning+to+30-pin
http://www.amazon.com/Imris-Connecto...ning+to+30-pin
A few of these outright do not support audio/video. The others don't mention whether they do.
^ Thanks Botond. Items 2 and 3 should do the trick to connect to my 30-pin iHome speaker.