The same all-in-one softcover edition and the same hardcover set as shown in Magpie's post and a set (plus an extra copy of TTT) of the Ballentine paperbacks. One TTT has a price of $1.25 and the other $2.50..hmmm the first is noted as "The Authorized Edition" but not the second. Not a big collector of anything but its fun to browse used bookstores and see what treasures are on the shelves.
I've got a paperback three-volume set, although it doesn't match because my original Fellowship fell to bits and had to be replaced (the others are heading that way - I should probably just buy a new three-volume set that does match), and a large, one-volume illustrated edition in French that I bought myself as a 21st birthday present. I used to have another one-volume edition which was printed on that very thin paper Bibles are often printed on, which made it ultra-portable. I took it to NZ with me - can't go off to live abroad without your favourite book, after all - but unfortunately it got soaked when I was sailing and I reluctantly threw it away.
I currently own the omnibus edition with illustrations by Alan Lee, a 3-book set from some time in the 1970's and the 7-book edition that was released around the time of the Fellowship's theatrical release.