You have a couple of obscured links off site that do not look like they should be there - I will flag this for staff attention -
In the mean time looks at the solutions below - also double check the passwords and security of your email account and make sure your PC does not have a virus.
The only “hacked” sites I have seen here have been people getting the password somehow to a site so you do want to be careful how you log in and use a tough password.
You should also check to make sure that someone has not added a new user to your site. Problems have also happened when there was more than one Admin. and an Admin left on less than graceful terms.
Dashboard >> Users
There have also been a few Posts on “hacked” sites and it was because someone got the Post by Email address and using the Post by Email to send in new Posts, if you have Post by email you can regenerate the address for that feature.
If you are really concerned you could as the staff to look at your site: http://en.support.wordpress.com/contact/
You could also use a secure log-in in case you are on an unsecured link: http://en.support.wordpress.com/https/
how many admins are there?