My favorite part of the museum was the display with a UFO and some aliens...I have a feeling that almost everyone who visits the museum has their picture taken in front of it.
If you're interested in the Roswell crash, the museum will help you learn everything you ever wanted to know about it. There is a ton of reading involved (Roswell Incident timeline, official documents, etc.), but if you don't have time to read everything, there's a great book in the gift shop, Witness to Roswell by Tom Carey and Don Schmitt, whose cover boasts that it's "the most comprehensive investigation ever made into the 1947 Roswell Incident." I read it and thought it was very informative, and I learned some things I didn't already know about the crash.
In the back of the museum, there is a section of wall covered with alien and UFO artwork and a model of an alien in a big glass tube.
Elsewhere in the museum, there is another one and a recreation of one of the crash victims about to be autopsied.
The section of the museum devoted to crop circles was interesting, and I really enjoyed the wall of alien cartoons...I wish they'd all been collected in a book and sold in the gift shop, so I could look at them whenever I want. The gift shop was the best museum gift shop I've ever seen...usually I don't buy much in museum gift shops because they're generally overpriced, but most of the items in the UFO Museum's gift shop were reasonably priced. I wanted almost everything in the gift shop, but since I could only fit so much in my luggage, I showed some self-control and only bought six or seven things.
I loved the International UFO Museum and Research Museum, and I definitely recommend it to anyone who is interested in the Roswell crash or just UFOs and extraterrestrials in general. The museum was very interesting and informative, and admission is only $5. Be sure to check out the gift shop and stop by the alien Coke machine on your way out. : )