Has your favourite wool sweater developed holes? One way to mend the hole, or to embellish a plain sweater, is to needle felt patches over the holes with a small amount of roving and a felting needle. Erica at the blog Honestly WTF has written a tutorial explaining how to make heart-shaped patches for your sweater elbows.
If you want to see a video of the felting patch technique, the one above demonstrates it well. You'll have the option of making the patches in different simple shapes, such as those found in cookie cutters (stars, hearts, trees, Easter chicks or eggs), or if you're feeling really artistic, in more complex creations of your own design: birds, insects, flowers, text, or whatever you like. If you wish to simply mend your sweater unobtrusively, you can try to find roving in a very similar colour, or if that's not possible, mend the sweater with the closest colour of roving you can find and then dye the whole item a new colour.
There are considerations to keep in mind. Felting won't work with synthetic fibres or with superwash wool. To be a candidate for felt patches, your sweater must be natural, non-superwash woolly fibres such as sheep's wool, alpaca, angora, or cashmere. The felt patch, while it may look unobtrusive, will have a very different texture from the rest of the sweater, so you'll have to ask yourself if you'll be okay with that or if you'll be constantly fingering that stiff, lumpy little patch. Needle felting involves fast, forceful stabbing motions within inches of your fingers, and you're bound to stick yourself with the barbed needle at some point in the process, and it will hurt a lot. Felting isn't a quick process, either — darning is faster. The video above, as you can see, isn't real time.
I've never used felt patches to mend my sweaters. I do mend my clothes whenever I can, but I mend knitted items by darning them with the same, or a very similar, colour. And generally my rule is that mending has to be invisible, or at least unobtrusive, or the item goes out. I'm really not into the grunge/Dickensian urchin look. I must admit though that those heart-shaped elbow patches would be adorable on a little kid's sweater, so there might just be some felt patching in my future.