Terrafirma is mapping tool for Terraria.
It gives block information in the statusbar as you hover, lets you zoom and pan around your map, and can save your map out as a png.
Click and drag, or use arrows or WASD
Hold shift to pan faster, hold control to pan really fast
Scroll wheel, or use Q/E
Mouse over the block to identify it in the status bar
Right click on chests and signs for more information