Such a loaded question, this one. What to read? What should I read next? There are lists upon lists, and hundreds of websites designed to answer just this question. But then, where does one start with these lists? Here are some of my favorite lists when I'm looking for a little inspiration...
Modern Library's 100 Best Novels: Established 95 years ago, Modern Library is an icon for readers. Their list is actually several lists in one, containing both a list of titles voted on by their board and another by their readers. They've also included a list of non-fiction, if that's your preference, and included the Radcliffe rival list. Now, these lists were compiled in 1997-98, but if you're looking for some classics that you've missed, or just a little inspiration or exploration in your reading list, this is a great place to start. (Note, this is the same list that the New York Times has printed, so why not go direct to the source?)
If you're really looking to broaden your horizons and try some authors you haven't heard of, check in across the pond with The Guardian (UK) list of 1000 books everyone must read. Divided by genre and including a great assortment of classics, modern classics, and popular titles (everything from Michael Crichton to Voltaire, mind-boggling), this is very comprehensive and really kind of fantastic. In fact, I'm tempted to make this one a challenge of some sort for myself in the future.
What I've found is that a lot of the lists out there are kind of highbrow and a little forbidding, with obscure titles or lots of titles that look like something a deep, thoughtful college student might carry around to attract some deep, thoughtful person of the opposite sex, pretending to read said title for fun. And really, while some of those titles are amazing, I'm not always interested in reading something that's going to be a challenge.
So my third recommended list is the best-selling titles of all time. There are actually some surprises on there, and a number of popular fiction titles, too. Worth a browse through, if only to stop and say, "Really? Seriously? THAT?!" a time or two.
Hope you've found a little inspiration, and happy reading!