I think URL shorteners came into place with twitter. The 160 character limit made posting the long URL's in the tweets difficult. You can use the URL shortener to shorten the URL.
The idea is simple.  Goto  http://goo.gl/ . Sign in with your google account. Then simply enter your long URL there in the text box. Then press 'shorten'. That's it! You get the shortened URL. The coolest part is that the URL is just 10 characters long.
You can also see the traffic to the URL's ie, the number of clicks etc also which is very useful. This can come handy when you place links of your files hosted in the file sharing servers in forms etc. You can see the stats of your file . Some file sharing servers do not provide stats in free accounts.
The main use is you have a shortened URL which can be easily included in tweets.
Other similar services:
www.bit.ly
www.tinyurl.com

Many of us may have noticed the attributes or properties that the mp3 files have- Such as the Album name, Artist, Song name, Track number, Comments etc. These are known as the MP3 TAGS. Most of us may have felt the need for modifying these tags. Windows media player does have the option to modify these and also you can do it on windows explorer by right-clicking on it, then->properties->advanced. But the problem here is that you have to do it one by one for each file which is very much time consuming and tedious. Here's where MP3TAG comes to help.

You can change the tags of multiple files in a single go! All you have to do is to first choose the directory in which the mp3 files are stored. They will be shown in the window with all the attributes.

Step1: Go to file-> change directory. Then choose the folder.All the mp3 files in the folder will be shown.
Step 2: Select the files you have to change attributes of in the files shown.
Step3: On the left side pane you can enter the mp3 tags you want to add. You have the option to choose which will leave the field blank or which will leave the field as it is. You can even choose an album art for the images. 
step4: Click the Save Tag button or select File-> Save. That's it.

Download MP3 tag editor: Visit this link. http://www.mp3tag.de/en/index.html

Enjoy modifying the tags!