BibMe.org
I think most high school, college, and grad students would agree that one of the most annoying parts of writing a paper is creating the bibliography. You spend all night punching out a 10 page paper and just when you think the worst is over, you come to the horrible realization that you still need to make a "works cited" list. This forces you to hunt down your references and figure out the proper format to use. It can be a pain, but luckily there are services online that can make building and formatting your bibliographies a quick, pain-free affair. Bibme.org is one such nifty service that takes much of the legwork out of creating bibliographies.
Thanks to Bibme's auto-fill feature, adding a reference is as easy as plugging in a title and hitting Enter. Bibme searches the title and gives you a list of matching books. Once you select the appropriate edition Bibme fills in all relevant bibliographic information. When the site can't find a piece of information, Bibme highlights the input field in red to let you know you'll need to find that info on your own.
Once you're done adding references you can save your bibliographies to your account, which makes keeping track of bibliographies from different projects easy. You can also download your bibliography as an RTF file in MLA, APA, or Chicago format. Once you download your bibliography all that's left to do is print it out and tack it onto the end of your paper (just be sure to delete the Created at www.bibme.org line at the end of the document).
I like the ease and simplicity of Bibme, but this service isn't comprehensive enough to handle more complicated projects. For a service that can handle all bibliographies, simple or complex,
Easybib.com witha $7.99/year upgrade to MyBibPro is the way to go. You can check out my full-review of Easybib.com here. Still, Bibme is a better choice when you just need to make quick simple bibliographies with little hassle.