I think it's best to just change your passwords now. I think all the affected sites implemented the update to fix the heart bleed bug, so changing your password should keep you safe.
I've heard from work that it is impossible to tell if someone hacked your information by exploiting the heart bleed bug because it doesn't leave a digital fingerprint.
When changing your password, try to make it different from your other passwords, so that if someone does get your password on one site, they won't be able to access your accounts on other sites.