1. Use Tabbed Browsing
With Tabbed browsing turned on in the Safari preferences (I enable all 3 options), you can have two or more sites open at the same time in the same window and simply tab between them. This is great when you want to read the content of one site and then go check something in another site. I use Tabbed browsing all day long. Couldn't imagine not using it. Another bonus tip is to right click on a link on a page and then have that link open up in a New Tab. This way you can still have the original page open while you read what was in the other link.
2. Mail this page
I use this option at least once a day. You can email someone a link, but you can't guarantee that they'll actually click on it. So in some cases I find it better to actually email them the entire page. This way the get the page that I want them to see and all of the content is live to be drilled down on further if they want. You can find this option under the File Menu, but I actually prefer to simply hit Command-I on the keyboard once the page loads. This will take you over to Apple Mail, create a new message and then put the page in the body of the message. At that point you can even edit out sections that you don't want to send like ads.
3. Use the Built-in RSS reader
Before Apple blessed Mail with an RSS reader, Safari was actually my RSS reader of choice. I created bookmark folder called RSS. Then I put subfolders in it for each category of feed that I was interested in. Then I would navigate to a site, and bookmark it's feed to that folder. Safari gives you a numeric badge count of the number of sites that have updated content since the last time you looked.
4. Create a bookmark button for your favorite sites
In addition to tabbed browsing, I also create bookmark folders for my favorite sites or the ones that I visit daily. As a matter of fact I have a "Daily" folder. It's the folder that contains all the sites I visit every single day. So In the bookmarks window I enabled the "Auto Click" box so that whenever I want to go to all the sites at once (loading in separate tabs), I can click that one button on the Bookmarks bar. If you click and hold down it's a drop down menu too so that you can go to any one site in the folder if you don't want to load them all.
5. The Back button is a menu
Everyone knows about the Back and Forward buttons present in every browser. You click a link, click a link, click a link and you then click back, back, back to go back to the first page. Well I'm going to save you some clicking. Click and hold down the back button and it will drop down a menu of all the pages you just went to so that you can jump back to a specific page!
6. Create a dynamic dashboard widget
Dashboard in Mac OS X is great to look at little pieces of information on the web all at once and without having to go to the individual sites. However, let's say you want to look at a portion of a webpage without having to go to that page every time. You can create your own webclip and it will not only be in Dashboard with the rest of your widgets, but it will update every time you go to Dashboard. Go to the page that you want to have in Dashboard. Then choose open in Dashboard from the file menu. Now you can click the section of the page that you want to be a webclip. Drag out the handles to get just what you want and click Add. Dashboard will fire up and allow you to add your new widget. Now when you go to Dashboard that clip will be there and update.
7. Use Private Browsing to hide your tracks
Whether you're on someone else's computer or a public computer or you just don't want someone to walk up behind you and see every site you've just visited, you can solve this by choose Private Browsing from the File menu first before going to your sites. This temporarily turns off Safari's history, caching, etc. I say temporary because if you quit and relaunch Safari, it will be off again. So it's really session based. However, good for those times when you don't want someone to know where you've just been, but you don't want to clear all history/caches.
8. Dynamically spell check your web input
Believe it or not you're inputing text in your web browser now more than ever. You could be filling out an online form, messaging on Facebook, posting a Tweet or doing webmail. So spell checking is important. You can turn on Safari's built-in "spell check as you type" feature to automatically spell check whatever you type into Safari from here on out. Just go to a site that has a text input field and right click into it. Choose Spelling and Grammar, then choose Check Spelling While Typing. From here on out Safari will underline in red those words not in the OS built-in dictionary.
9. Show Status bar
One of the things that I turn on immediately when setting up a new version of Safari or a new Mac is the Status Bar (found under the View menu). This puts a bar at the very bottom of your window and shows basically the status of a page loading (or not loading). I'm blind without it.
10. Get to your friend's websites quickly
If you're using Address Book to manage your contacts and you've entered their websites on their records/contact cards, you can access all of those sites right form the Safari Bookmarks menu using the Address Book submenu.