As much as I love digital cameras, in some ways I miss the unexpected and the unknown results of just doing strange things with my old SLR film cameras. In those days we'd use all kinds of little tricks to get creative images--like smearing petroleum jelly on a skylight filter to get soft focus (easier now to just call up the Gaussian blur filter in Photoshop) or holding a colorful piece of cellophane in front of the lens to get offbeat colors (much easier now in editing). One of my favorite things to do was to shoot two or more exposures on the same frame of film--just to see what kind of strange visual concoctions might pop up. Combining a shot of a sunset with a bold silhouette was a favorite double-exposure subject, of course, as was shooting a portrait of a friend and then shooting a distinct texture, like a rock surface. You can do the same thing incredibly easily in Photoshop, of course, by layering several images together, but to me it doesn't have the same experimental quality of not knowing what you were getting in the camera until you had the film processed. There was just something magic in not knowing what you might get--the lack of control was fun.
That's why I was happy when I bought my Nikon D90 12.3MP Digital SLR Camera (Body Only)to find that it had multiple exposure capability. Yippee! Back to the future! Using the feature is, to be honest, a little bit bogus--it involves going to the menu system and setting up the multiple-exposure (how many shots on one frame) which takes time. And it seems like you have to do it after each exposure series. There is probably a custom setting so that you can leave it in multiple-exposure mode, but so far I haven't gone looking for it. Of course, with my first SLR cameras, I actually had to physically rewind the film after each exposure to put another exposure on top of it, so that was certainly no easier! But I am glad to see the feature coming back to cameras. You may have the feature and not even know it, so take the time to look at your manual's index (you kept your manual, didn't you?) and see if there is a multiple-exposure feature.
I shot the photo here in my garden last summer on one of the first days that I tried the feature. All that I did was to set the camera up to take two exposures on one frame, then took one shot of a bed of zinnias and another of a bed of marigolds. The camera took care of underexposing each frame (by one stop, I'm guessing) so that when they were combined, they wouldn't be overexposed--something you had to consider in film exposures, too.
Perhaps it's a longing for my misspent youth, but I love finding features like this in digital cameras. Pretty soon there is going to be a built-in petroleum jelly effect and won't I be waxing happy!