Ah, springtime. Time to go outside (otherwise known as 'The big room with the blue ceiling'), and begin digging in the dirt, removing some plants and adding others. But if you want a great way to delay the actual "going outside" part, you can spend much time happily laying out your future garden with Plangarden ($20/year, 45-day free trial).
Plangarden can be launched directly from the Web or downloaded and run locally, but you must have an active Internet connection and a Plangarden account to log into the program. The primary advantage of downloading is that if you have a slow connection, you can work locally and only worry about connecting when you need to log in or save. (All of your data is stored remotely.)
Plangarden is fairly easy and intuitive, though there are online tutorial videos to watch. You lay out your garden in plots of various shapes and sizes, then drag-and-drop vegetables, fruits, and flowers. There's an extensive selection of choices, and you can set aside areas for individual plants, rows, and rectangles. You can also move around the text labels for easier or reading, or delete them entirely.
In addition, there is an extensive set of tools to track when you should plant (and when you should harvest), as well as a system to track what your actual harvest was.
In addition, you can have up to five 5-acre plots active and swap between them. Twenty five acres of total land area is thus available. Further, Plangarden stores previous year's plots, so you can compare total harvests over time.
Drawbacks? A Flash-based app, the interface is not quite Windows standard. I experienced some issues with the interface getting "out of sync" with itself, for example, selecting carrots but not having the drop-down menu update properly to present me with different carrot varieties. And, of course, since everything is saved remotely, any time you're without net access, you cannot get to your plots, charts, and so on. How much of an issue this is depends on how reliable net access is for you and how long any outages last.
Overall, I found Plangarden a very useful tool.
Note: The application itself is free, but it requires a subscription to the Plangarden service.