Tripod Dolly - For around $20 you can turn your GorillaPod into a fully adjustable dolly using 3 rollerblade wheels and some nuts and bolts. This straightforward project is based on CineSkates and only takes 10 minutes to build. It's effective and a whole lot cheaper than shelling out $200 for the real thing.
Improved GorillaPod Helping Hands Tool - This hack takes the idea of the Helping Hands tool (2 clips with a magnifying glass) and fuses it with a GorillaPod. It's an easy project that requires a drill, crocodile clips, epoxy and a piece of plastic for the base. After popping off some joints on the GorillaPod, crocodile clips were attached to the leg ends with epoxy glue. This Instructables user used an imitation GorillaPod to keep costs even cheaper.
How to Build a Light Up Camera Level for a DSLR - This mod adds a light up level to a GorillaPod. This helps you position your shot in low light, which can be useful since the GorillaPod is so flexible that it's easy to get a crooked shot. This mod requires a little soldering and wiring knowledge for the LEDs but overall it's a pretty handy mod for hardcore GorillaPod users.
Make Your Own GorillaPod - This project skips starting off with a GorillaPod altogether and walks you through making a DIY GorillaPod of your very own. Using inexpensive loc-line modular hose sections and some bolts, you can create a Gorillapod for less than it would cost to buy a real one. This similar hack takes the same idea but streamlines and improves it a bit.