This one is rather short, but basically I needed a regex string that could tell if what I was being fed was a web site or something else without actually going to said site. And really all I needed to check was that the data could possibly be a domain. That's it. So after looking at some of the more complex and most likely overkill examples out there, I decided to roll my own:

   1: /// <summary>

   2: /// Checks to see if a string is a valid domain

   3: /// </summary>

   4: /// <param name="Input">Input string</param>

   5: /// <returns>True if it is a valid domain, false otherwise</returns>

   6: public static bool IsValidDomain(string Input)

   7: {

   8:     if (string.IsNullOrEmpty(Input))

   9:         return false;

  10:     Regex TempReg = new Regex(@"^(http|https|ftp)://([a-zA-Z0-9_-]*(?:\.[a-zA-Z0-9_-]*)+):?([0-9]+)?/?");

  11:     return TempReg.IsMatch(Input);

  12: }

The code above simply looks for something starting with either http, https, or ftp and then  the domain, and finally the port if it exists. I could even use this to separate out the various parts if need be (just sort out the various groupings). So it's simple, straightforward, and probably a bit buggy, but it's been working on my test data which is enough for now. So try it out, leave feedback, and happy coding.