Here is an activity that I originally found in the book Math for Smarty Pants :
What is a $1 word? Start by assigning a cent value to each of the letters of the alphabet. Let a = 1¢, b = 2¢, c = 3¢, and so on up to z = 26¢. For any word, add up the cent values of its letters. A $1 word (one dollar word) is a word for which the cent values of its letters sum up to $1. To take a few examples, you may want to verify that "maximize" and "reciprocal" are $1 words.
In English, there are several hundred $1 words. If you want to check the value of a word, I have a one dollar word value calculator available. You can also view a (fairly complete) list of $1 words. This list contains nearly 1,000 words (966 words, to be precise), some of which are proper nouns.
Before you take a look at that list, though, here are some questions to try:
In case you're interested in words that are $1.10 words, you can find a list of them here.
A similar activity, but using multiplication, is Torment. You may also like math activities for kids and other word-related mathematical recreations.
Sources used (see bibliography page for titles corresponding to numbers): 32.
One final note: Of course, assigning values of 1¢ to 26¢ is somewhat arbitrary; one could assign other values, say $1 for an a to $26 for a z; in that case, one might be interested in finding "hundred dollar words."