There is a critical bug within OpenBSD's OpenSSL library that is used by pretty much every distribution of linux including Debian, Ubuntu, Arch and CentOS. This bug has been assigned CVE-2014-0160 and technical details can be found at The Heartbleed bug.

This bug has the potential of leaking your private keys and other sensitive information. Please update your OpenSSL to the newest available version (1.0.1e-2 deb7u5 or 1.0.1g on Debian) and regenerate your server keys.

At minimum you should regenerate your server hostkeys. You should probably also regenerate any OpenVPN or self-signed SSL certificates. Below are the steps to regenerate your server keys under Debian. Similar should work across any distro.

apt-get update
apt-get upgrade -y
reboot
/bin/rm /etc/ssh/ssh_host* && dpkg-reconfigure openssh-server
reboot

At Feral Hosting we began implement these fixes last night and have updated our status page to reflect this. Please note the new hostkeys.

This bug is considered critical and you should implement these fixes immediately.

Please upvote for visibility, self-post karma is useless

^{Edit: spelling}