Crowdfunding is an interesting idea: people who want to do some kind of project, build something, produce something, ask people on the net to basically give them money up front, in exchange for a reward/product if the project succeeds.
The upside for the person paying is usually to get the product early, at a lower price. The upside for the project is that they get funded without having to do much but present a compelling idea online.
The first thing I supported, that feels like a crowdfunding thing, was the Ada Initiative in June 2011 - this was the least product-like of the lot, as the main thing was supporting a good idea and a worthy cause, and the promised swag was of minor interest. I think it was a keychain and some stickers, but I actually never received them. After making them aware of this a couple of times, I forgot about it, and I don't mind much - I am listed on Seed 100 Funders-list. Making a lot of conferences adopt anti-harassment policies was a nice early achievement of the initiative.
The next thing was much more concrete: The Nixie Ramos Clock. Those nixie tubes are just cool! The project completed funding in April 2012, and had a delivery date planned for August 2012. I received my clock in September 2013, 13 months delayed.
While I was waiting for the Ramos Clock, I decided to give a little bit of money to the git-annex project, just because it sounded like a nice project, and it would be cool if Joey Hess could actually live from funds from around the globe. This was in June 2012, and the stickers that came with my little contribution came on time, and the development also proceeded on schedule, as far as I remember. I have no use for the stickers, and I haven't gotten around to trying git-annex yet, but still.
When I saw a project creating an electric mini guitar with three strings, I had to jump on it: The Electric Loog. The funding completed in November 2013, and they planned to start production in December, and wrote that they set a very conservative delivery date of May 2014. This was postponed. In the beginning of July the message was that they would be shipping very, very soon. The latest update says shipping is at the very end of July, with the guitar arriving in August. We'll see.
In January 2014 a colleague convinced me that the Danish project Airtame, building a wireless HDMI receiver (think Google's Chromecast, only working with everything, and with open source protocol and software) was cool. Their original plan was shipping in May/June, but that has so far slipped to October/November. Let's see.
So far all the things I have thrown money at has almost completely come through, but usually with a rather large delay in finishing, which is worth remembering.
It is interesting how something feels like it's free when 13 months expire from when you pay, and the product shows up. Except for the duty, tax and fees. So don't forget about those when backing projects outside the EU!