Short URLs become important when you need to share the address of a Web page. They are not only easy to remember and to key in, but also are very economical in using characters. But then they also pose a problem. You might not know what lies beneath the short URL.

Here's a list of some of the best URL shrinkers and also expanders.

1) is.gd (17 characters)

Pronounced is good, is.gd shrinks your URL into 17 characters by default. It also allows users to see the actual URL behind the is.gd URL. This can be done by adding a dash [http://is.gd/zU38-] to the end of the is.gd URL or by setting your preference by visiting is.gd. A no-frill URL shortener.

2) bit.ly (20 characters)

Three extra characters over is.gd, and bit.ly gives you the power to track your shared URLs. Get to know how many people clicked the link and also what pages are referring to it. Get an account to use it along with Twitter. If you really cared, bit.ly is the current default URL shrinker for Twitter.

3) cli.gs (20 characters)

It is one of the most feature-rich URL shortener. Cli.gs gives you a very comprehensive analytics for your short URLs -- number of times the short link was clicked, who all blogged about it or shared it over Twitter or Friendfeed or other social sharing sites, and lot more. It can also directly tweet the URL.

4) SnipURL (25 characters)

SnipURL has bit too many characters but worth it for the convenience of editing the URL to which the shortened URL will point to. It also gives you a list of popular links on the URL shortening site.

5) TinyURL (25 characters)

There were days when TinyURL actually proved its name. Though it will use some extra characters, it can be recognized by lot more people as it is the first popular URL shortening site. If you want to preview any TinyURl [http://tinyurl.com/qmae35] link, just add preview to it [http://preview.tinyurl.com/qmae35].

6) LongURL

LongURL will show your a screenshot of the page along with the URL to which the short URL is pointing. It can be used by visiting their site or by installing a Firefox add-on or a Greasemonkey script. [You know what Greasemonkey is, don't you?]

7) LongURLPlease

LongURLPlease does what it says, nothing else. Go to their website or install the Firefox add-on. Currently, it will give you the target URLs of links shortened by 65 URL shortening services.

8) Untiny

Untiny is another URL expander that supports a large number of URL shortening services. It can be used from within the browser by adding it to the search engine list. At least Firefox and Opera support adding search engines to the default search box. If you have Greasemonkey installed in your Firefox Web browser, you can also add Untiny Greasemonkey script. There are tools for several other platforms and applications as well.

Short URLs bonus

If you happen to use short URLs extensively, and also get lot of clicks on them, you might want to cash in on the opportunity. Switch to adf.ly for shortening URLs. Adf.ly will make money showing ads before loading the page,a part of which will go to you.