Being a sorcerer is awesome, and the most awesome way to be a sorcerer in Minecraft is with Thaumcraft. It's a vast mod that revolves around drawing the magical essence out of physical objects in the Minecraft world and reshaping it into new forms. In the process, you'll create altars, wands, golems and fill dozens of jars of coloured goo. There's even a puzzle game you'll have to complete to research new spells. Grab it here.
Another great mod for spicing up world-generation is Natura. It adds a wide variety of new tree types, and therefore different-coloured woods to make your home more aesthetically pleasing. It also adds a few extra crops for early-game food and resource production, and makes the Nether a little more dangerous. Natura is a nice first step into Minecraft modding, because it sticks close to the themes of the regular game. Grab it here.
Minecraft's default maps are a bit rubbish. They don't offer much detail, have to be pulled out and looked down at to use, and don't display anything other than where you are. JourneyMap fixes all that—it maps your world in real-time as you explore, can be displayed in the corner of your screen, and even lets you set waypoints to return to later. If you have a habit of getting lost in the wilderness, JourneyMap will get you home safe and sound. Grab it here.
Tools are the backbone of everything you do in Minecraft, and Tinker's Construct lets you make far better tools out of a much wider range of materials. They're upgradable, modular, and can be repaired if they break. Oh, and the mod also adds a smeltery to make high-end tools and increase ore processing efficiency. If you love having the best possible equipment to work with, grab Tinker's Construct from here.
If you like the agricultural aspects of Minecraft, you're going to love Forestry. It's a huge mod, which adds a bunch of new items, machines and blocks, but it's best known for its bees. You can become an apiarist, capturing wild bees and cross-breeding them using real genetic principles to create masses of different useful resources. If I were teaching biology, I'd be using this in the classroom. Grab it here.