Add Menu: Blender 2.5

Use Shift + A to bring up the Add menu. Spacebar no longer works by default in version 2.5.

Quad View: Blender 2.5

Use the View menu and choose Quad View to separate your view into 4 quadrants: Perspective, Top Ortho, Front Ortho and Right Ortho.

Split Views: Blender 2.5

Find the small diagonal lines in either the upper-right or lower-left of your view. When you hover your mouse over either of these two areas, a cross-hair cursor appears, indicating you are ready to split a view. Drag either vertical or horizontal to begin splitting, but as you experiment with this, you will see you are committed to the first direction you drag in.

Join Views: Blender 2.5

Use the same small diagonal lines in either the upper-right or lower-left of your view. If you are joining a view, you must use the corner that is adjacent to the view you want to join and drag back towards it. You will see the same "darkened arrow" from previous versions that indicates which view is going to take over the other one.

Drag in Tools/Properties: Blender 2.5

In a 3D window, if you hover over the small "+" inside a circle at the top-left and top-right of your view, your cursor will become a double-ended arrow. If you use the top-left "+" and pull to the right, you will drag in the Tool Shelf. If you use the top-right "+" and pull to the left, you will drag in the Properties panel. You may also just click on the "+" to make each appear. You can drag them back left or right to hide the panels. Note that these panels change depending on what type of window you are in. See below for hotkey toggles.

Tools Shelf Toggle: Blender 2.5

In a 3D window, use T to toggle the Tools Shelf.

Properties Panel Toggle: Blender 2.5

In a 3D window, use N to toggle the Properties panel. Note that this panel holds more properties than the former Transform Properties did.

Set Center: Blender 2.5

Use Shift + CTRL + Alt + C to bring up the Set Center menu. Use this menu to select Center New, Center Cursor or ObData to Center.

Circle Select: Blender 2.5

Use C to circle select; you no longer have to hit BB.

3D Cursor Reset: Blender 2.5 and below

Use Shift + C to reset the 3D Cursor at the origin. This is handy if you want to create your next object with its global position at (0,0,0).

Hide/Show Transform Gizmo: Blender 2.5 and below

If you want to toggle the visibility of the transform gizmo, hit CTRL + Spacebar and choose Enable/Disable.

Align Active Camera to View: Blender 2.5 and below

Have you ever navigated a view, found a good shot and wished your camera was set up to that shot? Well... you can! Position your 3D view the way you want it and press CTRL + Alt + NUM0. Your active camera will align itself in that direction.

Marquee Zoom: Blender 2.5 and below

If you want to quickly zoom tight into an area in your scene: use Shift + B, then LMB-drag in your view.

Region to Loop for Texturing

Here's a handy option when you're texturing and marking seams: select faces, whose total boundary around, you want to be the seam, then press CTRL + E and choose Region to Loop. This will select the edges around those faces, making it easier to mark your seams.

Select Linked Areas for UV Texturing

So you've unwrapped your model in the UV editor, and now you want to select all points on a single "island" of UVs. Hover your mouse over one of these islands, and hit "L" to see that all the points in that island will be selected!

Isolate your Model in 3D: Blender 2.5 and below

This is a fun one to try: hit Alt + B and LMB-drag in your 3D view. Then, rotate around in your view to see that there is a "3D projection" of your isolated model in the view. Hit Alt + B again to return to the normal view.

Render Preview in your View

When the occasion arrives that you only want to see how a portion of how your shot renders, use Shift + P in Object Mode to bring up the Preview box. Drag and/or resize this box in your view. Let the box sit in one place for a few seconds, and it will do a preview render of that section only.

Create Objects in Object Mode

If you don't like how every object created gets sent to Edit Mode by default, you can change this in the User Preferences window. Go to the top of the Blender interface, right beneath the menus and pull down the dividing line between these menus and the 3D view. Click on "Edit Methods" and switch off "Switch to Edit Mode" under the section titled "Add new objects:"

Quick Toggle for Vertices, Edges and Faces: Blender 2.5 and below

In Edit Mode, use CTRL + Tab to bring up the Select Mode menu. Then, choose which you want: Vertices, Edges or Faces.

Global - Local Orientations Toggle: Blender 2.5 and below

To change between Global and Local coordinate systems for your object, hit Alt + Spacebar to bring up the Orientation menu. Your options will then be: Global, Local, Normal & View. You can easily switch back and forth between Global and Local with this method.