The Chatzos Google Group: ** UPDATE** As of 3/9/11, the Google Group is now a forum.  You can find them here:  The Google group is no more. Starting by the Chatzos Lady, herself, the Google Group is really a support group for all things chatzos.  This is a great resource for tips, tricks, and chizuk.  The group does generate a lot of email traffic, so it may be wise to subscribe to the digest (I found myself getting a little overwhelmed by the amount of email... and then I felt inadequate when I read that someone had shabbos done...on Tuesday).

The Chatzos Lady:  Azriella Jaffe has become the queen of all things Chatzos.  Her website has some great info re: getting to Shabbos early and relaxed.  PS You may know Azriella from her book What do you Mean You Can't Eat at My House.  If you are religious and you have non-religious family (or if you are not religious and you have religious family), this is a MUST read. 

The Gift of Chatzos:  The chatzos ladies resource website.  Articles, forums, chizuk... everything you need to make chatzos happen.