Every once in a while I've noticed the number of processes I've got  
running jumps up a little higher than normal.  So I check it out and  
realize that I'm building up a bunch of processes that just aren't  
completing.  About half of the one's not completing say "SELECT  
waiting".  I'm not doing anything that I am aware of that could be  
blocking anything.  I am only doing regular vacuums.  I am not  
explicitly locking anything that I know of.  Is there a way to figure  
out what each of these processes are waiting on?