Its so simple.. Here's how it goes.I'm talking about photoshop.. I dunno other s/w..
Make a duplicate layer of the image to be mirrored.
Now goto edit-->Transform-->Flip vertical
Use the move tool to align the picture just below the original image.
Now decrease the opacity of the duplicate layer to a low value as required.
Final image will look like as shown below
You can do this for text layers also. A more beautiful mirror image can be created by selecting the lower portion of the duplicate image--> Right click on the selection--> Use feather--> Take a suitable radius(say,10 pixels) --> press "delete" --> You are done
The final image will look like as shown below..