Twitter has informed users that their service had been hacked and that 250,000 usernames, email addresses, session tokens, and encrypted/salted passwords had been compromised. According to Twitter's director of information security, Bob Lord, who posted on blog.twitter.com:
As a precautionary security measure, we have reset passwords and revoked session tokens for these accounts. If your account was one of them, you will have recently received (or will shortly) an email from us at the address associated with your Twitter account notifying you that you will need to create a new password. Your old password will not work when you try to log in to Twitter.
To date, I haven't received a notification for any of my accounts, but I've changed them all anyway. I'm paranoid, but I'd recommend you do the same, and use a password management app so you can set something strong and not have to worry about remembering it yourself.
If you were notified by Twitter about your password, let me know.