I have one something like the one Donna shows in her link. It's a Coghlan's brand 4-slicer and I got it at Wal-Mart. There is a slightly different style also that only makes 2 slices. I had one of those in the past and maybe it was a little nicer (in terms of not rusting and not needing to be folded to stow efficiently), but I really like the ability to make four slices. If I were only ever going to make two slices I might look for one of the other ones again.
One note is that when I am only toasting two slices, I wrap a patch of tinfoil over the space for the other two slices. This gets the two toasted a lot faster.
Edited to add: Went looking for one like my old non-folding 2-slicer and found this folding (what looks like a) 2-slicer from Primus. It's stainless which would be preferable to me to the Coghlan's one, which gets quite rusty.
Here is one more like my old 2-slicer (although mine did not have a handle sticking out to get in the way for storage; otoh that would not get hot when toasting maybe, which would be a bonus). This one is also stainless:
Now this one I have never seen before:
I like the look of it, and the home-invented-mom-and-pop-ness of it, but it doesn't look super space efficient (does not show it folding at all). At 5" x 9", I'm not sure if it is supposed to straddle two burners (?)
And here is one more, something like the above but a bit smaller and folds flat (the above one may fold, I'm not sure).
Now I'm hungry for toast!