If you regularly use a language that requires letters with diacritics -- such as á, ä, é, ë, í, ã, ñ, õ, etc. as they are used in Spanish, French or Portuguese -- and you recently switched from Windows to Mac OS X as I have, you might find this hint useful.
In Windows, while there were various ways to enter these characters, the best one of them was just to enter a ' and then the vowel, and you would get the accented version of that letter (in this example, the letter with the acute diacritic).
In Mac OS X however, if you set the keyboard layout to a language that has these letters (such as Spanish), you cannot use this trick; the only way of inputting these letters is the standard way supplied in Mac OS X (Option-e then e for é; Option-e, then i for í; etc.). I personally found this very annoying, and searched for quite a while on how to change this.
The answer is a lot simpler than I expected. If you use the US International - PC keyboard layout, you instantly get the fast way of entering the letters with diacritics back!
Go to System Preferences » Language & Text » Input Sources. Check the US International - PC input method in the list of Input Methods. (If you also use other Input Methods, uncheck the others or select the US International - PC method as the current Input Method.)
Now you can use the fastest way of entering these characters.
Mac OS X Hints
http://hints.macworld.com/article.php?story=Howtotypeletterswit20100304073426167