I use a mac (though this is not critical to the question, it has some relevance)
Every time I have to choose a password, I make a plain text with name of the website, username, and password in it.
Then store it in a single directory.
The directory though is not accessible by everyone, but it is encrypted (basically I created a .dmg file that requires a password to be opened). The "master password" itself is not stored anywhere and I remember it.
Is this a bad habit?
What do services like OnePassword offer more?
EDIT
I would like to know a little more so I would be grateful if you could go beyond the "Yes - No" answers :-)