Official Word
The Star Wars Insider #34 told us that Anakin's mother, named Shmi Skywalker, would be played by Sweedish actress Pernilla August. In that same issue Rick McCallum commented on Pernilla saying, "She has all the dignity and power that you could ever want for the role of Anakin's mother." The picture below, from the official site, shows Shmi and Anakin at the dinner table:
Delta Source: SPOILERS! Highlight area below to uncover them!
Delta informed us that Shmi would be present during the Pod Race scenes in the Mos Espa Arena.
Kivlehan: Most of the talk about this character has revolved around an old interview George Lucas gave back around 1983. He mentioned that in the original trilogy we had seen the "good father" Ben Kenobi, and the "bad father" Darth Vader; in the Prequels we shall see the "good mother" and the "bad mother". We assume Shmi will be one or the other.
Good mother or bad mother? I'd bet on Shmi being the good mother. Why? Because Episode I is supposed to be the feel-good movie and having a "bad mother" would undercut that good feeling, especially when the bad mother is the main character's mom!