The crossover between 'As The World Turns' and 'The Young & The Restless' (and by extension, 'The Bold & The Beautiful') is already taking place online in a series of webisodes called 'L.A. Diaries'. It details how Amber Moore first met Alison Stewart, and how they went into business together.
Ali will be joining 'As The World Turns' onscreen March 21st, and there is a promised TV crossover between the soaps on March 27th.
There are five webisodes up already, but I haven't seen any of them. I'm still a dial-up dinosaur here at Toobworld Central. But it's not like I'm missing much - Diane Werts of Newsday says that these 'L.A. Diaries' webisodes "don’t even meet the slapdash standard of one-take daytime drama". But still she says that if you need a quick soap fix while at your computer, you can't really go wrong with the "show".