A vulnerability has just been discovered in https, specifically in the Diffie-Hellman key exchange. This arose from the old export restrictions set by the US, so that its law enforcement and security agencies could break encryption used by foreign entities. Ars Technica, as usual, has a good write-up.
The researchers who discovered the flaw have a dedicated website which gives pointers on what to do if you run a web server, or just a browser. They have a server scanner, or you can use the one at Qualys SSL Labs.
Ivan Ristić has some more detail on increasing the strength of DH on Apache. Unfortunately, it may not be supported by the version of Apache you happen to have running.