1) Install the Opera Desktop browser on a computer (opera.com)
2) Open the URL opera:about
3) Copy the exact user agent onto a piece of paper
4) Install the Opera Mobile browser (from android market)
5) Open the URL opera:config
6) Tap inside the quick finder and type the word custom
7) Copy the Opera Desktop agent ID into Custom User Agent, and hit Save
Almost everything should work exactly as it does on a PC! I'll have to check, but this should even fool most video sites into working properly. If you want an adventure, use the Firefox Desktop ID and see if sites like Hulu will work.