Office Supply Screen Protector (for Nokia N800... dimensions will vary for the 770)

Supplies:
Clear plastic transparency (the type used for photocopiers).
Ruler.
Pack of post-it notes.

1) Cut a 5.9 x 9.4 cm rectangle out of the transparency. I suggest using a section of the transparency without scratches, bends, or rough spots.

2) Clean your N800 screen. Use the post-it notes (sticky side facing out) to get any crud from under the screen bezel.

3) Wipe off the transparency to remove any dirt.

4) Carefully work the cut transparency so that it fits between the bezel and the screen. I usually start with the transparency under the left corner of the bezel, work the other corners into place, then run my fingers along the edges to get them to snap in. Be patient and careful, and it will fit.

5) Check for crud between the screen and transparency. You're looking for particles that, when stuck under the transparency, could rub the screen and possibly scratch it. You may have to remove the transparency to get these out.

When you're finished, you will have the transparency sitting nicely atop and protecting the N800 screen. I have not noticed any decrease in touch sensitivity, although I've bumped the brightness up a notch as the transparency has a slight opaqueness to it.

no screen protector
no scratches
6 months of use

(I used a protector for 4 days and then the static it caused, caused the colors to go strange in the display. removing the protector fixed the colors)

I got by without a screen protector until, I noticed glare. Then, I got a Boxwave Anti-Glare Screen Protector.

It helps!
I experienced my first sratch after I applied the protector... Thank God!