If you're on Twitter, follow @2012TicketAlert - some peeps in Milton Keynes wrote a programme to monitor the 2012 ticket site, and it posts a message every time tix are released. I managed to get some dressage tix this morning for tomorrow's session via it, so can personally & highly recommend!
There's also an online alert programme - checker.benmarshinteractive.com.
It looks like you're new here. If you want to get involved, click one of these buttons!