Lots of applications for this simple command.  Yesterday, I was troubleshooting a SQL connection issue and even though I had enabled TCP/IP in protocols, I was still unable to make a connection.  As a sanity check, I ran a shortened version of the command below which showed me that 1433 was not open and ultimately brought me to the source of the problem. 

Launch a Command Prompt as the administrator (right click, CMD, select Run As Administrator).

Enter the following command:

Read more: List Ports in Use

You go to a web site, you want to download something and you're required to give an email address, possibly to confirm you're a real person.  In most cases, I create an alternate SMTP address on my mailbox, acknowledge their message and then delete the address from my mailbox.  As an alternative, this site enables you to create any email address and receive messages which can be viewed through their site.  Be warned, EVERYONE can access this email so I would only use it in cases when the received mail is meaningless.

http://www.mailinator.com/index.jsp

Read more: One Time Email Address

Life was simple with Exchange 2003 but as life goes on, newer versions of Exchange have appeared and what was once simple has become a bit more complicated.

One of the first gotchas you notice with Exchange 2007, 2010 and 2013 is the increased security and the challenges of connecting to Exchange remotely.  One tool that I find to be invaluable is the Microsoft Remote Connectivity Analyzer which can identify various issues with your configuration.

Read more: Microsoft Remote Connectivity Analyzer

If you work in the IT industry, you know regardless of whether or not the issue is on your end, you need to determine the location of the problem in order to prove your innocence.  ;)

When mail issues arise, we use:

http://mxtoolbox.com/SuperTool.aspx

There are quite a few options on their site but at the very least, you can see if a mail server is blacklisted.

Read more: MXToolbox

I bought a Dell tablet and I really liked it except for when I really needed to get some work done which is when I started hunting for a bluetooth keyboard.  Since I'd already purchased the nifty aluminum keyboard from Apple for my iPad, I connected it to my tablet.  All was well in the world until I started looking for my favorite Windows keys.  Stumbling upon this site, I found that 'some' of the combos work, others not so much but I still think it's helpful nonetheless. 

http://support.apple.com/kb/HT5636

The one that really drove me nuts was the Windows delete key which can be had by simultaneously holding the CTRL and D key.

Read more: Apple Keyboard Shortcuts

Did you forget to enable RDP to only discover your mistake after you were remote to the machine?  Me too.  If you can get on the network, you can launch the registry editor and then point it to the remote workstation.  Change the following:

HKLM\SYSTEM\CurrentControlSet\Control\Terminal Server\fDenyTSConnections

Set the value from one to zero.

Read more: Remotely Enable RDP