I was wondering if anyone knew of a suite of tools similar to those found in Unity3d, but for working with 2d games. I quite like the simplicity of getting Unity3d up and running. I hope there is something like what I am looking for...

Well..you could follow some Unity tutorials and work 2D magic in there.
Here's an article about how 2D Zombieville was created in Unity3D.

Or try Novashell

Then there is Power Game Factory

Blitzmax is worth a look.

Here's a tutorial for creating a pong clone for iPhone in xcode.

There's Love, but thats kind of cryptic, all scripting.
A community member was supposed to release an IDE for it a month ago, but hrm, nothing.

Then there is Verg-Rpg, thats pretty cryptic to.

Finally there is Torque2D, you need to register an account to get the demo.

Torque2D is the closest thing I've seen to 2D Unity. They have a free trial of it IIRC.

Thanks guys! Novashell is quite interesting, as is that article on Zombieville!

Torque2D is currently being rewritten from the ground up with a boat load of major improvements, and is due to be released sometime next year. It won't be compatible with the current version.

Also, Unity 3 will apparently come with more tools for managing sprites. It's due in the summer, and the base version will almost certainly still be free.