Here's a quick idea for a simple valentine - it doesn't use any fancy papers, special art materials or require any advanced technique.
The hearts on this valentine were created by dipping the heart stamp into a saucer of bleach and then stamping on colored paper. I used a stamp that I chiseled out of a gum eraser, but carving out a heart from a potato works just as well. The colored scraps of paper were from packaging materials - paper from junk mail (including the insides of envelopes) is another source of interesting paper options. A definition of "love" torn from an old dictionary completes the sentiment.
Proof positive that what speaks from the heart is the most important creative component.