Over the past few weeks I have seen an explosion in players on the tiny MuttsWorld modded server: tekkit.muttsworldmine.com
If you are starting to feel bored with wood blocks and iron blocks, you should really take a look at tekkit. It requires a custom client, but I think you will find it enjoyable.
More info below...
The client for tekkit can be downloaded here: http://www.technicpack.net/download/
1. Download : http://www.technicpack.net/download/
2. Run the Launcher.
3. Top left select Tekkit, and under options make sure you are using version 3.1.2
5. Add Server: MuttsWorld Tekkit tekkit.muttsworldmine.com