http://www.basketball-reference.com/friv/trades.cgi Pretty cool tool. Shows that teams do have certain "favorite hook-ups." Interesting that the Rockets have made so many trades (11) with the Grizzlies, which haven't been around for that long. This is true especially during Morey's (and his pal Chris Wallace's) reign. On the other hand, they've only made 1 trade with the Lakers (the T-Will deal in which the Lakers were peripherally involved), 1 with Charlotte (Baxter for Bogans) and 1 with Denver (Posey deal in 2002).
February 19, 2009: In a 3-team trade, the Houston Rockets traded Rafer Alston to the Orlando Magic; the Memphis Grizzlies traded Kyle Lowry to the Houston Rockets; the Orlando Magic traded Brian Cook to the Houston Rockets; and the Orlando Magic traded Adonal Foyle, Mike Wilks and a 2009 1st round draft pick (DeMarre Carroll) to the Memphis Grizzlies.
Another neat tool on it is that you can see every move a GM has made. For example http://www.basketball-reference.com/executives/dawsoca99x.html
You can trade for coaches as long as he is one of the Van Gundy brothers. http://www.basketball-reference.com/executives/smithot01x.html