Leave it to the Japanese to finally figure out a way to add cell phone charms to the iPhone, or just about any handheld that doesn't have a little loop for the charm to wrap around (which seems to be a must-have design option in Japan). The answer? Adhesive buttons. Just stick 'em on your phone (iPhone or otherwise) and wrap your strap/dongle/charm of choice to it.
This isn't an iPhone-specific thing of course, but I guess there are a surprising number of people wanting to attach a charm to the iPhone and realizing they can't.
The only problem is that it looks pretty ugly. I understand the whole cell phone charm thing and wanting to customize the look of your phone, but the adhesive button is just unsightly--it looks like your iPhone has a growth coming out of it.
Plus, once you stick it on, good luck getting it off. I recommend getting one of those colorful iPhone decals instead if you want to stand out from the crowd. But hey, if you're a charm fanatic, go ahead and get one if you can decipher the Japanese on the Strap-ya page. It's only $2.19 but the shipping is probably way more than that.