In an interview with the New York Observer, Eva Amurri stated that she will be doing nude scenes in the upcoming third season of Californication, which premieres on September 28. According to the interview, she will be showing her breasts and butt. Her first appearance will be in the second episode of the season.

Seemingly taking after her mother, Ms. Amurri said she’s comfortable with herself and didn’t hesitate taking the role.

“You basically see boobs and butt. It’s the same as you would see on a European beach. It’s nothing scandalous,” she said. “It’s just in our country everyone gets so worked up about everything like that.”

Also: “Men are naked as much as the women are on that show, which I really like. If you’re going to be naked, at least it’s equal-opportunity nudity,” Ms. Amurri said. “And you know, I’m 24. If I’m going to be naked anywhere, I should really do it sooner rather than later. It’s pretty much as good as it’s going to get.”

http://www.observer.com/2009/daily-transom/thats-amurri-sarandon-scion-prepared-role-pole-dancing-mom

According to some casting calls I found, there may even be more actresses doing nudity this season. Here is the casting call for the character that Alicia Witt plays:

[DR. DALY] 30's-40's. The beautiful lady that replaces Dr. Rad as Becca's Doctor. She kindly explains to Hank what is going on with his daughter while simultaneously slipping him her card in the hopes that the two of them might have an appointment of their own later on. Please submit all ethnicities. Some tasteful nudity and simulated sex required. Co-Star.

And here is the casting call for the character that Diane Farr plays:

[JILL ROBINSON] Jill is the 30 year old, neurotic, and slightly boy crazy grad student and TA to Professor Bates. Jill takes a liking to Hank upon meeting him, but warns Hank as well as herself that he could be
dangerous for her. Must have excellent comedic timing. Please submit all ethnicities. Some tasteful nudity and simulated sex required. Guest Star, 10-episode arc.

http://www.avsforum.com/avs-vb/showthread.php?p=16857502

While the descriptions do say "tasteful nudity", the casting call from Eva Amurri's character mentioned "tasteful nudity" also, and based on that interview, she shows quite a bit.