Camera / View:

Shift + Middle Mouse Button (MMB) to strafe.
Ctrl + MMB, or mouse Scroll to zoom out in.
MMB to rotate perspective camera.
Numpad keys for switching between various perspectives such as front, right and so on.
Numpad 5 to switch between ortho and perspective.
Num pad period (.) to center camera on selection.
Shift + C to move 3D cursor to center and frame all objects.
Z to switch between wireframe and solid display of mesh.

Edit mode: TAB.
Edit mode switch between face, vertex and edge: CTRL + TAB.
Create subsurf (in object mode) CTRL + 2/4.
Add loop cut to subsurf: CTRL+R.
Add edge by selecting two vertices and hitting F.
Add/Draw edge tool: K.
Select edge loop: Alt + RMB.
Merge two vertices: Alt + M.
Merge two meshes: Crl + J.
Add vertex to line: W -> Subdivide.
Set cursor to selected: Shift + S -> Cursor to selected.
Deselect all: A.
Select by rectangular region: B.
Shift + A to add nodes in node view.