I've had an Amazon Kindle for a bit over a year now. (Perhaps sometime when I'm less busy I'll explain why I like it as much as I do.) My grandmother, who has had one even longer, introduced me to a free game called Every Word, in which the goal is to spell as many words as possible, using the letters of some other, longer word. If you have a Kindle, I recommend it. Just remember that sera is really a word (the plural of serum).
If you don't have a Kindle, though, or want to play a simple word game in situations when obviously doing something on a Kindle would be inappropriate, here is the dark ages version. All you need is a piece of paper and a pencil or pen (or use the margins of your class notes, but pretend that I didn't say that).
Choose a somewhat long word or name, say, appendix. Make a list of all the three-letter words (not names or abbreviations) that you can from the letters of that word, a second list of four-letter words, a third of five-letter words, and so forth.. For instance, from appendix, you can obviously get pen, end, and pend, but you can also re-arrange the letters to make pie, axed, pined, and napped. When you run out of words, start over with a new word.
I have had a lot of fun with this recently, especially from Constantine and persuasion (35 three-, 62 four-, 47 five-, 15 six-, 2 seven-, and 1 eight-letter word before I got bored).