I guess I'm hard on cameras. On one of mine, bought 3 years ago, the LCD screen has a lot of fine scratches and one deeper gouge. Still works fine, though.
Because of the damage I was doing to that older camera, I've been trying out an eFilm screen protector/hood on my newer Canon 30D.
There are two versions of this:
One is a universal model, made to fit onto most cameras that share the same size screen. The universal model comes in 1.5", 2", 2.5" and 3" sizes, I think. It can be found in silver and black. It has a thin clear LCD cover that mounts onto the LCD with adhesive, then a removable folding hood which snaps into place on the frame around the clear plastic. I'm using a 2.5", black version of this on my camera.
The other model is a little more expensive and is camera specific. It attaches at least partially using the eyecup frame, replacing the original eyecup, and has some have "button" extensions built into them. By design, it is thicker. I tried it on the camera and felt it protruded too much, so opted for the slimmer, universal model.
My reason for buying this thing was not so much LCD protection, as it was for the hood that helps shade the LCD and make it more useful in bright outdoor situations. The hood folds flat when not in use, and, as mentioned, is removable.
Well, I won't buy another for my other camera.
The reason is that the hood unclips by sliding to the left from the base mount, and falls off *a lot* when carrying the camera on it's strap. It's really irritating and I've nearly lost the hood a few times. It should have some sort of positive lock to keep it in place. Currently I've got a couple small pieces of black gaffer tape keeping it in place. These help, but shouldn't be necessary.
On my older D-SLR (Canon 10D), I'd once installed a Hoodman protector/hood combo. The non-folding hood was always in the way and for all practical purposes had to be removed to use the camera. I lost it and eventually removed the clear protector/hood mount.
Since then, on that and other cameras that have them, I've protected various LCD screens with the thin, slightly self-adhesive plastic that comes in sheets, is widely available, and easy easy to cut to size and shape. These can be a little tricky to get installed without a few air bubbles under them, get damaged eventually, but work fine and it's no big deal to just replace them every once in a while. I bought a packet of ten sheets marketed by Kodak that has ben enough to cover and re-cover LCDs on three film cameras and two D-SLRs for 3 or 4 years now. There are a lot of different manufacturers offering these sheets, which are just like what is shown in the link jennyyu provided. Heck, the Wolfe Camera store three blocks from my house even offers them. If you want to protect an LCD screen, this is what I'd recommend, at least until eFilm comes up with an improved product.
BTW, Hoodman offers an LCD viewing loupe that might be a better way to both shade *and* magnify the LCD during playback and menu changes, or even with Live View, if you camera has it. I haven't tried this yet, but just might when I finally lose the eFilm clip-on hood.