I've always been a fan of crosswords. Since I was in college, I would do the daily crossword in the campus paper, sometimes during class, often between classes and if I was really close to completing it, I'd finish it up at home.
I've been feeling sick for the past few days and spent a majority of yesterday sleeping and drinking green tea by the pot-full. In between I did a few puzzles in a Mensa brain teaser/puzzle book my fiance and I picked up at Barnes & Noble a while back.
There is a Wordoku puzzle, which is like Sudoku but with letters instead of numbers — I erroneously thought I'd do better with letters, but I seemed to get more tripped up by it for some reason.
I don't remember the name of the puzzle I like the most, but it's two pages. One page has a list of questions. The questions are marked with a letter and numbered spaces are left for the answer. On the opposite page there is a crossword-like grid with a number/letter combo in each box. You answer the questions on the one page, then fill in the corresponding box on the next. When it's all filled out, it creates a passage from a book or a saying.
If I'm not up for reading, I find this is a pretty satisfying waste of time and since it makes my brain work harder than it would just watching TV or something, I don't really feel like I'm wasting my time.
I can't find the exact book to link to, but here is what Amazon came up with when I typed in "Mensa."