Rails made Web application development substantially more enjoyable. Surprisingly, even in Rails 2.3, there are some areas that still suck: Erb-Templates are the typical HTML/XML tag soup mess, CSS-Files are, well, CSS files. HAML and SASS are two technologies to fix this: HAML templates are concise and powerful, SASS makes writing CSS almost a fun experience. Be there or be width:20px height:20px.
Clipping is a handy way to collect important slides you want to go back to later.