LAS VEGAS — Forgot the in-box; get ready for the u-box.

As in universal e-mail in-box. In a speech Monday at the Consumer Electronics Show, Yahoo CEO Jerry Yang said the Internet company is opening up Yahoo Mail to outside developers to create an in-box that will combine e-mail, text and instant messages along with multiple social networking accounts on one page. In other words, whether you receive a text message or a comment on your MySpace page, it will all show up in your in-box. The new Yahoo (YHOO) Mail will also prioritize contacts according to how often a user communicates with them.

With “open” the catchphrase of the day, and rivals like Google (GOOG) monopolizing media attention with open standards initiatives like its Android mobile platform, Yahoo has embraced the zeitgeist an effort to regain momentum and create some buzz. On Sunday night, for instance, the Silicon Valley company announced it was opening up its mobile platform so companies like MySpace (NWS) and eBay (EBAY) could create widgets for its cell phone service.

As part of his e-mail demo Monday, Yang showed a mock message in which Yahoo co-founder David Filo asks him if he wants to meet up at a nearby burger joint. Yang dragged the e-mail into a Yahoo Maps icon found in the left hand bar of the page and a map showing the location of the restaurant instantly popped up.

“These are the things I think we can be doing more of going forward,” said Yang.

But Yang stopped short of giving an actual date when people can expect to see the Yahoo Mail of the future in their in-box. Yang’s demo was sleek and impressive, and a one-stop-shop for all of one’s communication needs makes sense. Of course, you can bet Google (GOOG) isn’t far behind — it recently opened up Gmail to outside instant messaging services like AOL.