If you use last.fm, eHarmony or LinkedIn I highly recommend changing your passwords and preferably using a different password for these sites and others.
For those of you not aware, there have been an increasing number of sites reporting security breaches, resulting in the leak of user and password data. LinkedIn, eHarmony and now last.fm are all a part of the latest wave of compromised data (as noted by The Verge).
These 3 sites aren’t alone. Sony, Zappos, Microsoft, Twitter and many other major brands have reported their own security breaches and compromised data.
So, if you have an active account with any of the affected sites I highly recommend changing your password. I also recommend creating separate passwords for your vital accounts and information online, especially your email and financial accounts, which can be used as gateways to gain access to other accounts and personal information. Microsoft also has a brief, but good article on strong passwords (and a good tool for checking password strength).
UPDATE: FormSpring has just announced today (7/10/12) that their site has suffered a similar security breach, and that they will be disabling some 30 million affected user accounts.