Also, a Google search would've gave you many possible tutorials, that could help you get started and when you run into trouble, then you post a specific question about the part you're stuck on. Here's
one decent tutorial. Also, you're gonna need a web service or something to get the job done for you, not just ASP.NET. I also know that you can send the sms through email, by some carriers.
The below is taken from
Tech-Recipes.com.
T-Mobile: phonenumber@tmomail.net
Virgin Mobile: phonenumber@vmobl.com
Cingular: phonenumber@cingularme.com
Sprint: phonenumber@messaging.sprintpcs.com
Verizon: phonenumber@vtext.com
Nextel: phonenumber@messaging.nextel.com
where phonenumber = your 10 digit phone number
joedeene