As already mentioned, The Pinball Hall of Fame in Las Vegas is probably the most well known collection on a national level. Pittsburgh has two good collections-- Pinball PA, with various solid states up to modern machines, and Pinball Perfection, with more old (wood rail) tables and rarer tables like Banzai Run and the often-broken Circus Voltaire.

There is a growing number of public collections of modern Stern/Jersey Jack/CGC/American/etc. typically in barcade or enthusiast collections made public environments-- like The Pinball Garage outside of Cincinnati (the owner builds/built vpin cabinets), The Pinball Museum of Corbin in rural KY (50 or so modern tables, mostly Stern) or The Asheville Pinball Museum. They will all vary in quantity and quality (both in games and maintenance)-- so use Pinball Map and see where your favorites (or rare tables) are actually at.

Visual Pinball X and Zen Pinball are probably the two most prominent emulators.

If anyone likes other coin operated esoterica, Marvin's Marvelous Mechanical Museum outside of Detroit is worth a visit. Lots of 19th-early 20th century rare mechanical attractions and maybe 10 new pinballs.