Word Box: Cut slips of paper. Ten, twenty... a hundred even. Write one word on each slip of paper. Nouns and verbs work best, but adjectives are also OK. Put the word slips in a container of some sort (I use a small, plastic box shaped like a Chinese takeout container). Here are some exercises you can do with your word box.
Generic: Shake the box to mix the words around. Pull out three-five slips. Write a scene using each of those words.
Fibonacci Story: Pull 6 words. Write a story in 13 sentences according to the following rules.
First word you pull = 1st word of 1st sentence
Next word you pull = 1st word of 2nd sentence
Next word you pull = 2nd word of the 3rd sentence
Next word you pull = 3rd word of the 5th sentence
Next word you pull = 5th word of the 8th sentence
Last word you pull = 8th word of the 13th sentence
[Note: you can also do this exercise with a 13-line poem]
Taboo: Pull one word. Write a short scene in which the main character is unable to say that one word you just picked. Here's the catch: this character is in a situation where it's imperative he/she use this word. Example: The character is a look-out sitting in the ship's eagle's nest who, for some reason, can't say the word "pirate." He has just spotted the mast of a ship on the horizon, and it bears a pirate flag. You cannot use "pirate" anywhere in the scene.
These are just some ideas, but the possibilities with the word box are endless!