Dirt

Dirt is a very common resource found almost anywhere on the top five or ten blocks. A portal can turn one dirt block into a workbench, which is then used to make other benches for crafting. Digging a dugout in dirt is a good idea for your first home in a new world. Alternatively, if you spawn near a hill, you can burrow into the hill and use the ground surface for shelter. Although dirt may seem useless, it makes a great starter building block. Great for your blockhead's first house. And, dugouts make perfect temporary homes/checkpoints when you're traveling. And, if you warp in another blockhead while the other is journeying, dugouts are PERFECT if you want the newly warped in blockhead to catch up to the other.

Using a spade to mine dirt, there is a chance that the dirt block will also drop one worm.

Since the 1.7 updated, now there is a Dirt Dodo that when slain, it will drop a Dirt block.