5-10 I guess. I tend to use passphrases rather than passwords, since they're easier to remember (and more secure).
Stuff like "A H05tage 2 4Tune" or "A R00m w1th A Vi3w"
Also some which are longish words in a very obscure language that I happen to speak.
They're all on my Palm in an encrypted database (and written on the back flyleaf of Volune 5 of Churchill's "History of the English Speaking Peoples")
Actually, writing passwords down isn't that much of a security risk so long as you don't write them on PostIt notes and stick them to the screen.