If the domains are currently in your name and you transfer them to an LLC you are correct that you must receive (and declare) compensation for the domains. However the amount of that compensation could be very small as even among professionals there are huge differences in opinion of what individual domains are worth. To cover your arse in case of an audit you might get a second or third opinion on the record that the value you have assigned to them is accurate - then have the LLC pay you for the domains, or provide you with a note (IOU) for them, if the LLC currently doesn't have any money. You could also loan money to the LLC and then have the LLC buy them with cash - that would be how I would do it. Then pay yourself back with proceeds from future sales or domain parking etc. Each of these structures (and others I didn't think of) would have different tax consequences you should consider.
I'm not a tax attorney, though in speaking with mine about how to structure my LLC my understanding is that the above is pretty accurate. Definitely consult your own professional before making any final decisions though.
P.S. Anybody considering this would be wise to look at the structure Frank Schilling and Xedoc Holdings both have. Not going to say any more on that...