Resolve.org - this is a great website with a wealth of information about infertility and infertility related events. You can even find local support groups in your area through Resolve's website.
Infertility FAQ's - another link to Resolve, only this will take you straight to their Frequently Asked Questions. Again, this is a great resource for information about the disease of infertility.
Infertility Etiquette - this is a GREAT resource to share with friends and family about what to say or not to say to their loved ones struggling with infertility.
Take Charge of Your Fertility - another excellent resource with lots of information, chart galleries, forums, and even a book (which is free on Kindle by the way!)
Fertility Friend - if you are interested in charting, this is the best site to use. I've always used the free version, but you can upgrade to VIP which will grant you access to many cool features.
Stirrup Queen's Blogroll - this is the most comprehensive list of infertility blogs I have found. And she's even sorted them by topic!
Infertility Acronyms - if you are new to the online infertility community, you may have noticed that most of us speak in "code" which can be very confusing to newbies. Back when I first entered this community, I was very confused for a long time, until I found this comprehensive list and was able to decipher what everyone was talking about! Now it's second nature to me, and I see these acronyms everywhere, in the most unexpected places!