I've searched a while and haven't found many patterns, so my intention is to give you a good selection of my own ideas as my site grows. Here I'll tell you what you need to know to alter a regular pattern so you can felt the finished article successfully.
If you haven't tried felting yet, check out this information before you read on. It's so easy to felt wool, you simply must try it.
You know, felted crochet is really versatile. You're not limited in what you can do with felting. Because the process thickens and toughens the crocheted fabric, it's suitable for all manner of items.
There are different levels of felting. You can lightly felt an item by only using the hot wash once then a cold rinse, or you can wash your item 4 or 5 times in a hot wash and take it to its shrunken, thickened limit before 'fixing' it with a cold rinse.
The more you felt an item the less the individual stitches will show - it will look more like a fabric.
Think about the item you want to make and its final use. Just as you're unlikely to use a fingering weight sock yarn for a tote bag, you wouldn't want to make a lacy stole from the bulkiest yarn you can find. It simply wouldn't work.
Check out this great information about how to determine the 'weight' of your yarn, ie. fingering, worsted, bulky, etc.
Be aware that although you can use a regular pattern to crochet something you want to felt - you should use one size larger hook (if you crochet tightly) so that the wool has some space to shrink, otherwise you could end up with something really thick and tough.
The easiest items to make in felted crochet are those which don't need to be a certain size, for which gauge doesn't matter. You can, however, make hats, mittens or any number of items to certain sizes, but you must be sure to check the gauge before you start your item.
You can do this by crocheting a swatch or tension square in the stitch used in the pattern. Treat this sample exactly as you intend treating the finished item regarding felting.
You must make a note of the...
You now have the information you need to alter the pattern to suit your felted crochet item.
Compare the before and after measurements to work out which size instructions to use. Say your sample was 12 stitches = 4 inches before felting and 12 stitches = 3 inches after felting. You want your hat to fit a 21 inch head.
21/3 inches (after felting measurement) = 7.
Check whether the pattern has a size which matches your 84 stitches around the widest part of the hat and off you go. You must also be sure to check the number of rows so that your hat will be long enough.
So - now it's time to get going on your own felted crochet project.