If you want to know all the inside-outs of Google, have a look at the Google guide. In the mean time, have a look at stuff below for quick reference.
Refining your search
You might already be familiar with Google's advanced search operators, but it nevertheless worthwhile checking Google's cheatsheet. For instance, I didn't know you could use ~ to look for synonyms, * as a wildcard for whole words or .. to use numranges in your search.
Conversions and calculations
You can use Google's search box for unit and currency conversions and calculations, check this screencast.
There is a lot of useful and interesting blogs and sites out there. It is kind of hard to keep up with them. I do so using Google Reader. You can subscribe to the sites you are interested in and then read the updates in your reader. Here's how.
Customized Search Engine
Google allows you to create your own search engine, that will only look in your preferred web sites. A great way to search all your trusted web sites with a single click.
