So far, YouTube has taken baby steps in mobile, launching with select videos available through Verizon Wireless’ V CAST and with device-specific applications such as the Helio Ocean and the Apple iPhone.

But now the Google-owned company is throwing open the doors, offering YouTube for Mobile with access to tens of millions of videos. Users will be able to engage with the site wherever they are, with many of the usual features found on YouTube.com. However, getting access requires a streaming-capable phone as well as a 3G operator.

It’s a big launch for YouTube; it’s not tied to one single operator, and you don’t need one specific device to use it, says YouTube Mobile Product Manager Dwipal Desai. YouTube estimates its service will work on more than 100 million devices worldwide.

Users will be able to access features such as their YouTube accounts, Favorites and the ability to upload from mobile devices and share videos on both m.youtube.com and youtube.com, the company says. Users also can rate and comment on videos directly from their phones.

The service will work with a streaming-capable phone and 3G service, which in the United States primarily means AT&T and Sprint Nextel. The service doesn’t work with most Verizon Wireless phones except some smartphones, Desai says.

In late 2006, YouTube announced its first strategic distribution agreement with Verizon Wireless V CAST for accessing a selection of YouTube videos exclusively for a limited time. But that only included a sampling of the most popular videos.

Desai says the mobile experience isn’t designed to take away from the online experience. The expectation is most people will use the mobile service when they’re away from their PCs, waiting in line or on a bus, for example.

YouTube also is offering YouTube for Mobile via a free downloadable Java application for a limited number of phones, including the Sony Ericsson k800, w880, Nokia e65, n73, 6110 navigator and 6120 classic.