Check out these links:
http://partysuppliesshop.com/60s/
http://www.party-oz.com.au/Party/60s.htm
http://partyplansplus.com/partyplans/60'sPlan.htm -- for their "60s/70s Age of Aquarius Party Theme" page. They have lots of ideas. Actually, some of them are actually 70s stuff, but they will work for you.
http://www.oldtimecandy.com (a great site)

Tell people to dress in costume -- you'll get everything from Kennedys to early 60s "American Grafitti" era greasers to astronauts to British Invasion/Carnaby Street to civil rights movement to late-60s/early 70s hippies (a lot of people think of the Vietnam era first half of the 70s as the sixties, and I suppose in a way they were! Think peace signs, smiley faces, etc.)

Music is EASY. The only trouble you'll have is choosing your era, as noted above -- Rock & roll, Motown, British, bubblegum and more are all "correct." You can switch every half hour or something. Maybe your library has some compilations? Do get the originals, not recent covers by modern bands. Decorations are easy, too -- Pick your era and go with anything from "Mary Poppins" and "The Graduate" posters to lava lamps and psychedelic posters.

Food should be fun. The site I gave you above just went with what they seem to consider "hippie food," but I think you can be more creative than that. Probably no one will want to drink it, but I would definitely serve the beverage that says 60s like nothing else: Tang! (If you can still find it). Fondue was popular both late 60s and early 70s. See if you can find "Screaming Yellow Zonkers." Fritos, and potato chips with Lipton "California" onion dip are easy and cheap. I doubt you could find Bosco or "Fizzies," and I'm not sure you'd want to!

A caveat about the above: If you guests weren't really around (or old enough to know what was going on) in the 60s, they will respond more to what they THINK of when they think of the 60s -- Beatles, hippies, and the antiwar movement; granola (really more 70s) instead of Tang -- than what those of us who were around then actually remember would. Like "Screaming Yellow Zonkers" -- they might not be worth the expense for a younger crowd who won't feel a nostalgic rush! (Although they are good).

So here's another spin for your husband's party. What things can you come up with from the CHILDREN of the 60s? Tang and Mary Poppins (and tons of other family movies, especially those huge, overproduced musicals unique to the era) are a start. Twister. Barbie. GI Joe. Super Balls.

Have a groovy time!