Here are some of the many contenders for the lateral moves most significant for either the hiring or losing school that have transpired over the last academic year (including a few that have been announced, but won't take effect till January 2006); others that I've missed should be noted in the comments:
Kenneth Abbott (international) from Northwestern to Arizona State.
Frank Bowman (criminal) from Indiana/Indianapolis to Missouri.
Curtis Bradley (international, foreign affairs law) from Virginia to Duke.
David Caudill (evidence, property, postmodern theory) from Washington & Lee to Villanova.
Stephen Choi (corporate) from Berkeley to NYU.
Mary Crossley (health law) from Florida State to Pittsburgh (to become Dean)
Mechelle Dickerson (bankruptcy) from William & Mary to Texas.
Jody Freeman (environmental) from UCLA to Harvard.
Michael Gerhardt (constitutional) from William & Mary to North Carolina.
Philip Hamburger (legal history) from Chicago to Columbia.
Valerie Hans (law & empirical social science) from Delaware to Cornell.
Geoffrey Hazard (legal ethics, civil procedure) from Penn to UC Hastings.
Samuel Issacharoff (civil procedure, voting rights) from Columbia to NYU.
Derek Jinks (international) from Arizona State to Texas.
Leandra Lederman (tax) from George Mason to Indiana/Bloomington.
Daryl Levinson (constitutional) from NYU to Harvard.
Clarissa Long (intellectual property) from Virginia to Columbia.
Lawrence Marshall (clinical, criminal) from Northwestern to Stanford.
David McGowan (intellectual property, corporate) from Minnesota to San Diego.
Miranda McGowan (antidiscrimination law, statutory interpretation) from Minnesota to San Diego.
Jennifer Mnookin (evidence) from Virginia to UCLA.
Mary O'Connell (international) from Ohio State to Notre Dame.
Stephen Perry (torts, jurisprudence) from NYU to Penn.
Jennifer Robbennolt (law & psychology) from Missouri to Illinois.
Edward Rubin (commercial, administrative, jurisprudence) from Penn to Vanderbilt (to become Dean).
Scott Shapiro (jurisprudence) from Cardozo to Michigan.
David Sklansky (criminal procedure, evidence) from UCLA to Berkeley.
Lawrence Solum (intellectual property, jurisprudence, civil procedure) from San Diego to Illinois.
Kent Syverud (insurance, professional responsibility) from Vanderbilt to Washington University, St. Louis (to become Dean).
Frederick Tung (corporate) from Loyola/LA to Emory.
Rebecca Tushnet (intellectual property) from NYU to Georgetown.
Aaron Twerski (torts, products liability) from Brooklyn to Hofstra (to become Dean).
Letti Volpp (immigration, law & culture) from American to Berkeley.
Joan Chalmers Williams (feminist legal theory) from American to UC Hastings.
Timothy Wu (intellectual property, Cyberlaw) from Virginia to Columbia.
My ten most significant (and leaving my own school to one side) would probably include: Abbott, Bradley, Choi, Hazard, Issacharoff, Perry, Rubin, Syverud, Williams. Comments are open, and are being pre-screened for relevance and content. Because I'm on the road, there may be some delay in the appearance of the comments.