Yeah, I've heard much about the Foundation books over the years. I'm not sure why I haven't read them.
I also think I'm going to finally read Hitchhikers guide. I bought it awhile back, but haven't gotten around to reading it.
A lot of my friends have been trying to get me to read Hitch too. I will soon, it probably has that blend of humor you're looking for.
Curious, why'd you rule out the Star Wars stuff? There're TONS of books and some of them are quite good.
Another direction (though fantasy, sorry) are the Drizzt books. They seem like quick reads and are plentiful, suggesting high adventure type stuff