per the WaPo:
The Orioles wanted to upgrade offensively at first base, but without many viable options, they chose to bring back the popular Millar, who gained fame with the Boston Red Sox. Now the Orioles are likely to focus their search for offense on left field. They remain interested in several players, including Cliff Floyd, Jay Payton, Aubrey Huff, Jose Guillen, Trot Nixon and Ryan Klesko. The Orioles aren't serious bidders for Red Sox left fielder Manny Ramirez.
For more on these stories, including the pursuit of backup catcher Paul Bako, and the latest on the Willilamson and Bradford signings, see this Sun article and this article at the official O's website.
Here's a nice quote from the Sun article to entice you:
"I made a decision, that Baltimore is where I wanted to be. I want to be an Oriole," said Millar, who said he also received interest from the Boston Red Sox, New York Yankees, Los Angeles Angels and San Francisco Giants. "I didn't want to play any games. They said they wanted me back and I wanted to be loyal to them. I think this team has made some great acquisitions and I want to be part of it. This is as excited as I've been in a long time."