Here are some of the cool Garduino-esque projects people have created:

1. Fish's network-connected Garduino.

2. Morrildl's YouTube build diary videos: entries, 1, 2, 3, and full-grown.

3. Properduino, a similar Instructable on starting seeds with computer automation.

4. Garduino upgrade, now with more Twitter!

5. Indoor Grow Space Automation Part 1