Implementing SharpSpell 3.0 within your project is as easy as adding a control to your Visual Studio 2005 Toolbox and dropping it on your form.
After you drop it, just set a couple of properties and you're done. Here's an example:

Then drop it on your ASP.NET Form and it will automatically add Real-Time Wavy-Underline Spell-As-You-Type Spell Checking to every Multi-Line ASP.NET TextBox control on the page.
If you don't need spell checking for all of the TextBoxes, you can use the .ControlsToCheck property to specify which controls to enable spell checking on.