Spring framework is complex, especially when you develop a real project with industry standards. Reading tutorials is a good way for learning at the beginning. But finally, you still need to read code from real projects. Luckily, there are some very good open source projects that use Spring framework.
Here are some open source projects that use Spring framework. By reading the code, we can get an idea of how to use Spring framework.
Alfresco Content Management
Spring Rich Client
Luigi Open Search Engine
Java Small Business Platform
You can also convert the source code directory to html page. There is a tool for that: http://www.java2html.com/download.html
If you know some other good projects, you can leave your comments below.