I really enjoy ribbon embroidery. You can cover a whole lot of area much faster than with thread embroidery, and there are lots of effects which you couldn't do with thread.

Here are a few more resources for supplies and books:

Ribbons:

River Silks produces incredibly beautiful hand-dyed ribbons in 4mm, 7mm, and 13mm widths. It retails in 5m spools.

YLI has a line of embroidery ribbons in 2mm, 4mm, and 7mm. It retails in 5yd spools.

May Arts produces 4mm, 7mm, and 1in ribbons in a small range of colors. It retails in 200yd, 50yd, or 30yd bolts (depending on width).

Hedgehog Handworks sells YLI and Gloriana hand dyed ribbons.

For those who'd like to dye their own, Dharma Trading Co. sells plain white silk ribbon in several widths.


Books:

The Handbook of Silk Ribbon Embroidery by Ann Cox is by far my favorite silk ribbon embroidery stitch guide. It's a small-sized book, spiral bound so it lays open while you're working, and her writing and photos are very accessible to the beginner. She covers a good range of stitches and flowers.

If that's not enough for you, A-Z of Silk Ribbon Flowers, also by Ann Cox, will carry you the next step. This book never drew me in like the Handbook did, but there are several techniques covered here that aren't covered in the Handbook, such as painting your ribbon (either before or after it's been stitched) to give shaded and ombre effects.

Your local library might well have some books on ribbon embroidery; it's worth having a look there. A quick search on Amazon for 'ribbon embroidery' brings up plenty of different options depending on your taste, such as this neat Encyclopedia of Ribbon Embroidery Borders or Embroidered Alphabets.

Good luck, and have fun!