If you enjoyed Nagel, pick up 'The Mind's I', an anthology edited by Douglas Hofstadter, which includes a few of Nagel's essays and many others of value. If you're interested in things like crime and punishment, Leo Katz has written several highly accessible books on moral philosophy and law, though his arguments sometimes trike me as glib. Reading Plato, especially the dialogs of Socrates, can be a little indigestible at first, because he takes a long time to get to the point. but there's a reason that Whitehead said most philosophy consists of 'footnotes to Plato'; once you get used to the style you'll find the weighty matters leavened with a surprising amount of dry humor.
Since you mention Hofstadter, I simply have to bring up Godel, Escher, Bach. Especially for anyone who's interested in computers and artificial intelligence, this is a must read. It is brimming over with philosophical issues, and is very accessible even to someone without any previous exposure to philosophy.
I'd also recommend "The Cyberiad" by Stanislaw Lem. It's an anthology of hilarious science fiction stories, many of which deal with deep philosophical themes. Also, along those lines is Douglas Adams' Hitchhiker's Guide to the Galaxy trilogy, which is also hilarious and very philosophical.
These aren't exactly the first books most people think of when asked for intro to philosophy books, but I think books like these are quite perfect as very easy, gentle, funny and fun intros to many philosophical themes. Their humor and wit also put the vast majority of "real" philosophy books to shame.
A colleague of mine with a background in semiotics recently read Godel, Escher, Bach, and said it was, among other things, to his surprise a good introduction to something very similar to semiotics, but independently derived by Hofstadter from first principles.
If you enjoyed Nagel, pick up 'The Mind's I', an anthology edited by Douglas Hofstadter
Edited by Douglas Hofstadter & Daniel Dennett you mean ;-)
Daniel Dennett's philosophical writings on consciousness/AI and religion are also very approachable. His "Intentional Stance" is a classic IMHO. I've not read all of his later stuff - but Consciousness Explained is also very good.
(His four Fs definition of life always cracks me up - fight, flee, feed, and... mating...),
