The spherical shape of dew and rain drops make them perfect for refraction photos but if you don't fancy shooting in your garden, you can have a go at this technique from the comfort of your living room. All you need is a clear surface - a CD case will do the trick – a colourful object to position under it and a pipette or water bottle to squeeze a few droplets of water onto the clear surface. As a side note, if your water drops aren't completely spherical it can distort your refracted image so don't knock the surface you're working on once you have the drops in place. You'll find a macro lens useful for this technique and extension tubes will get you closer to the drops but they're not essential.
Once you've chosen your flower, book, sweets etc. position it behind the water drop(s) and position your tripod so the drop(s) can clearly be seen through your viewfinder. If you're working out in the garden and there's a slight breeze, try using a Plamp to stop your subject swaying. As you want the background to be thrown out of focus so the water drop is the centre of attention, pick an aperture that sits in the lower range and make sure you're focusing on the refraction of the object in the water drop. If you're working with more than one water drop or just want to completely ensure your refraction is as sharp as it possibly can be try focus stacking. In a nutshell, you need to pick an aperture that will give you the best image quality, focus manually, then take a series of pictures, moving the plane of focus slightly further through your subject on each picture. Just don't move the camera or your subject in between shots as they won't stack correctly. For more details on Focus stacking read John Gravett's tutorial on Focus stacking images in Photoshop.
Flowers are a popular subject for this technique but have a play around with a bowl of colourful sweets or how about lining up a piece of text so certain words jump out through the water drops? Just remember they'll appear upside down so you'll need to flip the image.