Formulário (upload.html)
<html>
<body bgcolor="#FFFFFF">
<form method="POST" enctype="multipart/form-data" action="upload.asp">
<input type="FILE" size="40" name="FILE1"><br>
<input type="FILE" size="40" name="FILE2"><br>
<input type="FILE" size="40" name="FILE3"><br>
<input type=submit value="Upload!">
</form>
</body>
</html>
Script de Upload (upload.asp)
Dim objUpload
Set objUpload = Server.CreateObject("aspSmartUpload.SmartUpload")
objUpload.MaxFileSize = 150000
objUpload.Upload
x = objUpload.Save("/diretorio")
Response.Write "Upload efetuado com sucesso"
Documentação do fabricante: http://www.aspsmart.com/aspSmartUpload/
Veja também: Proteção contra upload de arquivos maliciosos