I spent six weeks in Argentina learning Spanish, and I'd love to keep up my limited skills by reading in Spanish. But, the fact is, my vocabulary just isn't good enough, and whipping out a dictionary at every other word is too cumbersome.
With a few relatively straight-forward changes, the Kindle 2 could really help out here. Amazon (or some clever hacker) could modify the existing dictionary to do translation. When you hover the cursor next to a Spanish word, an English translation of the word would pop up.
The technology behind this doesn't seem so tricky. The Kindle 2 already has a dictionary that operates in much the same way: when I hover next to an (English) word, a definition pops up. Thus, Amazon would just need to swap out the English dictionary for an Spanish-English dictionary.