Do you keep a small spiral notebook full of lists? Which books you've read, which books are next in a series, new authors you want to check out? Or maybe you've got an elaborate Excel spreadsheet, tabbed and color-coded by genre?
Well, try out two online databases, FictionDB  and FictFact , that not only let you keep track of what you have read, but also what you're reading now and what you're planning on reading. You can search by author, title, series, and more. Each database lets you rate the books and has an extensive new release calendar for tracking newly published titles.
There are some unique features to each database as well. FictionDB allows you to create lists, import and export book titles, and search your own books separate of the entire website. FicFact is actually designed specifically to track series books. Once you've set up which books in a series you've read, the database tells you which title is next on your reading list. FictionDB also has one really great extra feature, an email alert when a new book by one of your authors is added to the New Release list.
Image from http://www.pbs.org/parents/booklights/booklists.jpg