Google Spreadsheets has a powerful add on called Google Forms that allows a web developer to add simple forms easily to web sites in order to collect data from users.
This article discusses the way to embed these into a web application.
I've also created a Youtube video with a running commentary, screenshots and so on.
The examples above are adapted from a fully functional site and this article assumes a reasonable existing knowledge of HTML/Javascript/CSS in order to use these code snippets.