Since they opened the SDK you've been able to do most (all?) the stuff people were initially excited about. The problem is that all the excitement has long since died away so very few people are developing versatile Chromecast apps... and the ones that are out there are mostly buggy and poor designs.
AllCast [1] is probably the most well known despite being crippled (limited to 1 min playback I think?) unless you pay.
[1] https://play.google.com/store/apps/details?id=com.koushikdut...
hm...... i've been assuming that even tho there's an SDK it is still a turf war. if it's actually open to open source development... woah. many possibilities...