Let's review. Observe the following tidbit of information:

http://www.felbers.net/blogger.html

What do we call the preceding?

A URL. Easy enough.

A URL is not a citation for an internet source.

Why is it not a citation? Because it does not credit an author or work. A URL simply tells you the location (protocol, server, and file) of the information you’ve cited.

Using a URL and only a URL as a citation is the equivalent of using a Dewey Decimal System notation (or whatever indexing system your library uses). If you've ever written a paper, you know that

306.7 J925d
is not adequate for a citation, especially when your intent is to show that you are referencing a specific work by a specific author. For example,
Judson, Olivia. Dr. Tatiana’s Sex Advice to all Creation. New York: Metropolitan Books, 2002.
is a more appropriate way to cite the source, as it clearly credits the person and the published work.

Allowances are made for the unique circumstances of digitized information published on the Web—so, yes, the URL is important to include, but only as part of the full citation.

So then how do I cite an internet resource?

Various disciplines use varying formats when it comes to capitalization, ordering, and italics. You can find suggested formats from the American Psychology Assocation, The Council of Biology Editors, and the Modern Language Association, for example. The following style is based on the Chicago Manual of Style:

Author's name, "document title," Web site name. date of Internet publication. <URL> (date of access).
(Note: to create angle brackets here on e2, you'll have to type "&lt;" and "&gt;" around the URL in order to render them correctly.)

Here are some examples of applying this format:
Capezzutti, Cheryl. "The National Lint Project." Studio Capezzutti. 9 September 2002. <http://www.studiocapezzuti.com/lint/lintguys.htm> (1 November 2002)

Felber, Adam. "The State of the Union Drinking Game! (2003 Edition)." Fanatical Apathy. 27 January 2003. <http://www.felbers.net/fa/2003/01/27/the-state-of-the-union-drinking-game-2003-edition/> (31 January 2003)
Note: for a blog, like Felber's above, the first day the entry appears, it's at the main URL (www.felbers.net/fa) but that's a temporary URL. The bottom of a blog entry may note "Permanent Link," (or "permalink". In the citation above, the permanent link is used
Sometimes one or more of these pieces of information may be missing, such as a credited author:
Neo-Futurists. "Neo-Futurism." Neo-Futurists Web Site. 3 July 2002. <http://www.neofuturists.org/neofuturism.htm> (19 November 2002)
Or more commonly, the date of Internet publication:
Rockett, Wade. "Philosophus Stone Against The Cult Of Terror!" Wade Rockett Home Page. <http://members.aol.com/waderockett/pstone01.htm> (15 November 2002)
In any case, the date of access should always be included, because pages on the Web can change, move, or disappear altogether.

Wikipedia has tackled the problem of citation and the date of access head on, becuase the collaborative nature of the wiki involves various revisions over time, so they have a unique solution. The most current version of an article uses a simple URL, but in citing a Wikipedia article, the permanent link should be used (accessed by a link in the left column of the screen). Each time the page is updated, a new permanent URL is generated. For example, when searching Wikipedia for information on "brontosaurus," the first URL you would encounter would simply be:

http://en.wikipedia.org/wiki/Brontosaurus
but you would not use that URL in a citation. Using the permanent link feature, for example, early on January 6, 2006, you would include this URl in your citation:
<http://en.wikipedia.org/w/index.php?title=Brontosaurus&direction=prev&oldid=34171951>

However, a citation of the same article four months later, (visited on April 6, 2006, would have a different permanent link:
<http://en.wikipedia.org/w/index.php?title=Brontosaurus&oldid=47092564>

The unique ID number in the URL allows a citation to reference a particular revision of an article current to the time it was referenced (allowing readers to see the exact same version of the Wikipedia article as the author citing it, even though it may have changed in the intervening time).

Occasionally, you may need to cram extra information into the citation, such as in the case of a review:

Dana De Zoysa, Review of Dr. Tatiana’s Sex Advice to all Creation, by Olivia Judson. in Curled Up with a Good Book, 8 October 2002, <http://www.curledup.com/tatianas.htm> (28 October 2002)
Or an in-print article that you've accessed online:
Wallace, David Foster. "Tense Present." Harper's Magazine. April 2001. <http://www.findarticles.com/cf_0/m1111/1811_302/72732951/p1/article.jhtml?term=%22david+foster+wallace%22> (19 November 2002)

Citation of non-WWW resources

Email
Some reference style manuals do not consider personal communications "citable," because they are not publically archived and cannot be verified by scholars. But if you do want to cite an email, you can, using the Subject line as the title of the document referenced:

Mike Aba, "URGENT PLEASE REPLY," 29 April 2000, personal email (3 May 2000).
An email from a listserv might be locatable, so you can include the listserv in the citation:
Doyle, Ina Valeria. " Re: help - manure stories," 16 September 2002, <STORYTELL@VENUS.TWU.EDU> (15 November 2002).

Usenet/Newsgroups

Ereneta, Tim. "No Improv at My Wedding," 31 July 1998, <alt.comedy.improvisation> (29 August 1998).
Note that in the absence of a real name, the email address of the poster is listed.
<blackout@404infomagic.net> "The Ballad of Eskimo Nell," 31 October 2001, <alt.slack> (19 November 2002).
Note: as mkb pointed out to me, Usenet postings all have a unique identifier in the header which, if included in the citation, would make it more accurate. You could add in angle brackets, <6pt036$6p0$1@agate.berkeley.edu> to the first citation and <VbUD7.513$be5.63974@news.uswest.net> to the second-- placing the Message ID between the Subject and the Posting Date. However, the arbiters of citation, including the APA, CBE, and MLA do not prescribe the use of the Message ID, perhaps in the interest of removing clutter from citations.

IRC or other real time communication

Rhodes, Katherine C. 10 March 2001, group discussion, <irc.slashnet.org>, #everything, (10 March 2001)
Finally, if you are citing an internet resource in a published paper, it's a good idea to check the URLs again before publication to make sure they still work, to give your readers a shot at accessing the same source material you've used.



Additional sources:
Harnick, Andrew and Eugene Kleppinger. "Using Chicago Style to Cite and Document Sources." Online! A Reference Guide to Using Internet Sources. 25 October 2001 <http://www.bedfordstmartins.com/online/cite7.html> (28 October 2002)