We run a small ISP. I have a client with about 200 employees.  Because
of the nature of their business, these employees often need to send
rather large files to their customers. (It should be noted that these
employees are mostly novice computer users.) When they attempt to
e-mail these large files to their customers, they often encounter
problems because the recipients have e-mail systems that reject files
that exceed a certain size.  Also, these employees often want to send
these 15-30 MB files to dozens, and sometimes hundreds of people,
further exacerbating the problem.

We're looking for a web-based application that would help us with
this.  We host their Windows 2003 domain controller and Exchange 2003
Server.  I would like to run a web server that would allow the
employees to upload their file(s) and then send the URL to these
file(s) to their customers rather than the entire attachment.  It
sounds like a great idea, but I?m encountering ease-of-use issues.  I
thought about creating a user folder on a web server and letting each
employee ftp their files to the server.  Then they would just send a
URL to their customers that would look like this:
http://servername.example.com/username/filename.foo
Unfortunately, I?m afraid that this process would be far too complex
for most of these employees.

I?ve been looking for a web based application that would allow a user
to log in, upload a file to their directory on the web server, at
which point the web application would clearly display the URL of that
file back to the employee so that they could copy and paste it into
their e-mail.

I have run across a couple of apps that are close...

http://www.seattleserver.com/httpfs.htm
This still looks a little too complicated and it does not allow you to
authenticate with Active Directory.

http://www.http-com.com/
This allows you to authenticate with Active Directory, but it doesn?t
appear that there is any provision for making a file anonymously
downloadable, nor does it appear to spoon-feed you the URL of a file.

Beyond these two apps, I haven?t found anything that even comes close.
 I just need the employees to log in to a website with their existing
Windows 2003 account, upload a file using their web browser, and get a
URL presented to them that will allow anyone to download that file.
That?s it.

What is the name of an application that would run on a Windows 2003
Server under IIS that allow me to accomplish this?

In trying to find a solution, you could do an end around. 

create a private webpage. that page allows login to a storage area
where the files are placed. the emails sent to clients list the login
codes to access the private page(s).

file size limits can be managed by A) having a large buffer space
behind the webpage, i.e., (10 times the largest file anticipated)times
(overlap factor for file residence time in multiples of space - 1x,
1.5x, 2x, 3x) and B) a residence time in the storage space appropriate
to access by all involved and then the file is removed.

files can be FTP'ed into storage, and click accessed out.

Since you're using a Windows 2003 Server you may want to take a look
at using Sharepoint Team Services (not to be confused with Sharepoint
Portal Services).  A Windows Sharepoint Team site can be installed
free on Windows 2003 and is perfect for the sharing of documents.

brrich-ga, jgarrison-ga,

Thank you very much for the suggestions. Requiring the end users to
enter login information was considered too cumbersome from the get-go.
 However, Sharepoint Team Services does show some promise.  It's
overkill for what their needs are, but if it is able to do what we
need it to do, it might work.  One of my techs has worked with it in
the past and is currently installing it in a test environment to see
if it does the job.  I should know early next week if it's workable.

Thanks again for the courteous and helpful responses. 

-Chris