I'm constantly behind in planning out my garden. Maybe it's because I have moved from zone 4 to zone 6, so everything comes just a bit earlier; more likely, it's my deliberate, perfectionist, and yes, procrastinating personality clashing with an activity that's a bit more here-and-now. At any rate, I was pleased to discover SproutRobot, a site that reminds you when to plant your vegetables.
You can simply enter your zip code on the home page to see a week-by-week calendar, or create an account, to receive email reminders to start the plants you check in your profile. They also have paid memberships, where they mail seeds to you at the right times. The calendar includes instructions for each plant. These are geared toward the beginner, but having everything laid out by date might appeal to more advanced gardeners, too.
Here, it's already time for me to start my tomatoes and peppers. Lacking a lot of sunny indoor space for pots, I'll be trying this method using milk cartons as mini-greenhouses.
Other gardening links I've been enjoying: