There are actually a number of different Museum spaces, but you get into all of them for the price of one ticket. The sections are:
1. The Palazzo Nuovo which houses a collection of Roman sculptures including the restored original equestrian statue of Marcus Aurelius which formerly stood in the center of the Campidoglio square (certainly the most famous equestrian statue in the world).
2. The Palazzo dei Conservatori which houses an even larger collection of ancient sculpture, the sumptuously decorated apartments of the "Conservatori", and the Capitoline Picture Gallery (Pinacoteca). Constantine's giant head is once again available for touching in the courtyard.
3. The Palazzo Cafferelli directly behind and connected on all levels to the Palazzo dei Conservatori, which holds still more antiquities.
4. A tunnel under Michelangelo's grand Campidoglio square which connects to the ancient Roman Tabularium (archives) which is directly below the Rome city government building at the back of the square.
The view over the Forum from the Tabularium is among the best you will find anywhere -- equivalent to what you can see from the top of the Farnese gardens on the Palatine hill, but from the other end of the Forum. You can get into the tunnel and to the Tabularium from either the Palazzo Nuova or the Palazzo dei Conservatori. (The Tunnel/Tabularium has brand new wheelchair lifts and the Curator said on June 8 that similar lifts have been ordered for the whole museum complex. There are elevators to some areas, but some of them would be too small for a wheelchair.)
On the top level of the Palazzo Cafferelli is an exhibition on the restoration of the famous bronze statue of the "Capitoline Wolf" which suckled Romulous and Remus. The original statue is on display along with lots of other Capitoline Wolf stuff and exhibits of how the statue was restored. Step through the "Wolf display" area and onto a terrace with a nice cafeteria/restaurant (many sun umbrellas and some indoor seating, spotless rest rooms here and several other places around the Museums) and a great view of Rome toward the River -- you can't see the Forum from this side. If you look down on the back side of the terrace you can see the ongoing excavations at the base of the Temple of Jupiter Optimus Maximus that stood on the south-western peak of the Capitoline Hill.
There are two bookstores, one in the Palazzo Nuova and another in the Palazzo dei Conservatori. Both offer normal Rome Museum bookstore items, heavy on what is displayed at the Capitoline Museums. You can get into either bookstore from the Campidoglio square, without buying a ticket to the Museums.
Museum tickets and AudioGiudes are available at separate cashiers within both bookstores. Tickets cost 15,000 Italian Lira even though the brochure that comes with the ticket says IL 12,000. The ticket is for all of the Museum spaces, although you'd be really hard pressed to see everything on just one visit -- a minimum of three visits would be about right if you just want to see everything. If you want to contemplate or study what you are seeing, it would take many more. The Capitoline Museums are not as big as the Ufizzi in Florence or the Vatican Museums, but there is a lot more than anyone can absorb, perhaps in a lifetime.
The AudioGuide is available in several languages including English and Italian for an additional IL 7,000. The Audioguide itinerary, which lasts at least two hours and fifteen minutes, just skims you through the major pieces, but it is still worth the price. It starts in a long corridor at the back of the bookstore in the Palazzo Nuova, takes you through the Palazzo Nuova, then the tunnel and Tabularium, and then back up into and through the Palazzo dei Conservatori on the opposite side of the square Neither the Pinacoteca nor the Capitoline Wolf exhibit are included in the AudioGuide, but there are good descriptive signs in English and Italian throughout both of those exhibit areas.
Internet links (not meant to replace a visit to the museums!):
All of the major works are listed separately on the Internet at various art sites: Look in your guidebooks, find the name of the piece you want to view, and enter it in your Internet search engine. For example, http://www.altavista.com/cgi-bin/query?pg=q&sc=on&hl=on&act=2006&par=0&q=%22capitoline+venus%22&kl=XX&stype=stext gets you about ninety Internet pages that refer to the Capitoline Venus through the AltaVista search engine, and http://www.altavista.com/cgi-bin/query?sc=on&hl=on&q=%2B%22marble+faun%22+%2Brome&kl=XX&pg=q finds you 131 pages that refer to the Marble Fawn, including several that link you to sites about Nathaniel Hawthorne's novel of the same name which uses the statue as its central image.
For information on the equestrian statue of Marcus Aurelius, try http://mywebpage.netscape.com/mmdtkw/VMAurelius.html.
Information on the Capitoline Picture Gallery is at http://www.museionline.it/eng/cerca/museo.asp?id=2320
But don't use the Internet! Go to the Museums! But not on Sunday if you can avoid it: huge crowds and long lines in the hot sun on the square. Go some weekday morning at 10 AM, opening time, and plan on lunch in the museum restaurant about 12:45. That's the way to do Rome.
P.S.: Did you know that the name of the god Jupiter is just a Latin vernacular corruption of Zeus Pater, which just means "god (Zeus or Theos) the father"? "Jove", another name for the same god, is perhaps a later corruption of Zeus, based on the fact that there was no letter "u" in Latin. The "u" in "Zeus" became a "v" and the "Z" became a "J". Jove was also often identified with the Roman god Iovis (which may have been pronounced "Yoewis"), who, in fact might never have been a separate guy at all. He, like Jupiter/Jove/Zeus, always had a thunderbolt in his right hand. By Jove!!!