Here's a friendly reminder from Starwars.com.

"Last month, Del Rey Books and starwars.com opened up the suggestion box for Jacen Solo's Sith name to appear in the Legacy of the Force book series. With the galaxy once again approaching the precipice of war, Jacen sees a solution that will bring order to the chaos. That solution requires him to fully embrace the dark side, become corrupted by its influence, and emerge as the newest Dark Lord of the Sith.

Star Wars fans will supply the "Darth name" for Jacen, which will appear in the fifth book, Sacrifice by Karen Traviss. The submission period ends today at midnight (Eastern time), so it's your last chance to get in the Sith name of your choice. After tonight, a staff comprised of editors at Lucasfilm and Del Rey, and the authors of the Legacy of the Force series, Karen Traviss, Aaron Allston, and Troy Denning, will choose the top five entries from all the eligible submissions received within the deadline. On January 23, 2007 the top five entries will be listed on starwars.com for a fan vote. Voting will be open between January 23, 2007 and February 27, 2007."

You can find out more here.