I distinctly remember seeing a tutorial on how to do this, but I can’t seem to find it at the moment. So, I’ll write what I remember from it. Maybe someone will come along and post the link.
Since you’re new to Blender, I’ll try to be as precise as possible, but I assume you know generally what you’re doing since you’ve decided to take up a project like this.
Add a plane and delete the left two vertices. Subdivide it sufficiently so it looks like a pretty solid yellow line. Six or seven times should be enough. It all depends on how big the laser is going to be; the bigger the laser, the more subdivisions you’ll need.
Go into the Material Buttons (F5) and create a new material. Change it to Halo (under the Shaders tab). Select the HaloTex option as well. Now go into the Texture Buttons (F6) and add a new texture. Select Blend as your Texture Type from the menu. Click Sphere.
Go into the Colors tab and click Colorband. Make sure Cur (for current) is at 0. This will control the outside color of the laser. Change the A (for alpha) to 1. Make it red. A good thing to do so the core isn’t too thick is to move it around so its position is around 0.7. Change the Cur to 1 and make it white.
If you do a test render now, you’ll find that it probably looks pretty freaky. Don’t worry; go back to the Material Buttons (F5) and increase the Add to 1. But now if you render it, it’ll probably be too big (it depends on the size of course). To fix this, decrease HaloSize. Somewhere around 0.15 should be good.
If you did all this right, you should end up with a white line surrounded by red–a classic laser look. Fiddle with the Colorband, HaloSize, and Add settings to get the look you want.
If you have any questions, don’t be afraid to ask. That’s what we’re here for.
[EDIT Oct 6] [Added F# hotkeys.]
Here are some tips on animating it:
Move the vertices so one of the endpoints is the object center (or select an endpoint, Shift+S: Cursor -> Selection, tab out of edit mode, and click Center Cursor in the Edit Buttons (F9)).
Move it around and insert a Size keyframe where it will start “moving.” At the point where it comes out of whatever it comes out of (if anything), scale it down to zero (0). In the Material Buttons (F5), decrease Alpha to zero as well and insert an Alpha keyframe (I with the mouse in the Buttons Window) so it’ll be invisble before that point. As soon as it becomes fully “extended” from the thing it comes out of, increase Alpha to 1 and insert an Alpha keyframe. After it hits the missle, if you want it to disappear, insert and Alpha keyframe before it disappears (Alpha at 1), then change the Alpha to 0 and insert a keyframe.
I apologize if that seemed a bit hard to follow. Please ask if you need any clarifications.
[/EDIT Oct 6]