To begin, there are two pledge levels that I forgot to mention before, but I’ve seen them for nearly every project I’ve joined, so they’re deserving of mention:

“$1”: you want to help out, but you just want to “get your feet wet”. For that you can pledge a single buck. It brings no perks with it, but it still helps the project move forward a bit. Dozens of such a pledge still add up.
“$5”: a larger bid with a sole perk: mention of your name in the Thanks, whether it’s a special page in a book or comic book, or on a page on a Website (I’m listed on all 3 on different projects) …or whatever form it takes.
One thing: the Thanks are a part of every Perk level above $5 as well.
Where a project really gets cool is when it raises more than the target amount. Why?
Stretch Goals
After that amount, the folks who made the project add new features to their projects.
Take for example Grimtooth’s Ultimate Traps Collection. These were a set of books that I read years ago in my game life…. traps in fantasy gaming of a darkly humorous bent. For this project all the out-of-print volumes will be collected in a single hardcover volume. [I backed this]
Stretch goals included new books in this series, extra cloth bookmarks sewn in, even new backer-submitted traps.
Another example: a book that I backed made an audiobook version.
If the projects are the meat-and-potatoes then stretch goals are the neat desserts.
Crowdsourcing Sites
This is the site that I used for my novel, but I think that I’ll use another one next time. I used it because of the flexible funding option available.
Flexible funding means that you get the funds collected — minus their fees — immediately, so even if you don’t make your target you still have something to start to work with.
Traditional thought is that if you don’t make your goal you don’t have to produce your project — but in my case I don’t agree with that philosophy. Some people did back me, and I’ll finish my book as that’s what they paid for. Even though it’s taking me much longer than I’d like, I’ll get it done.
Kickstarter Website
You may have heard this mentioned a lot lately. Several films and TV shows were funded through this, as were many other projects. Two of my friends got funding for comic books through this, and many, many other projects.
Unlike Indiegogo, pledges collected here are only charged if the project funding target is made. As a result, if the funding goal isn’t achieved the amount collected is an even $0.
There are other crowdsourcing services, but for my needs they aren’t suited: Fundrazr is Canadian which suits me, but it’s better-suited to more altruistic projects than mine. Patreon is, as the name suggests, a way to become a patron-crowdsourcer ongoing to an artist. I’m not *that* prolific. That wouldn’t be fair to my contributors.
One thing is for sure: whatever service that you go with you have a lot of promotion to do.
Related articles
Crowdsourcing Mornings: Dream Writers: A Television Show
5 Creative Kickstarter Projects That We Love
Where Do We Stand: January Comics and Graphic Novel Sales