To start with, you don't need to jailbreak your iPhone to use these tips. They come right out of the box starting with firmware 3.1.2. Even though you might know some of them already, I'm sure there something in here for everyone and that's reason enough to have it posted here as Tips & Tricks.
Safari Tip #1: Navigating Websites - Show Destination URL
The first one's the easiest one. Tapping and holding on any link within Safari for just a few seconds will show a pop-up overlay with the destination URL. If an image is linked, meaning it leads to some webpage, you can apply the same technique to it.
Safari Tip #2: Navigating Websites - Open Link In New Page
The tap-and-hold technique can be applied to open the link in a new page as well. After you get the nice pop-up screen, choose Open In New Page and Safari will open the link in a new window, and you can continue browsing from there. If at any time you want to return to one of the previous pages, choose the numbered icon on the lower right hand side that displays how many windows you have open. Flip to the one you want.
Safari Tip #3: Navigating Websites - Page Up & Page Down
Double-tapping towards the bottom of the screen will re-center the page around your tap, basically bringing the page down. The only thing to note here is to not tap a link or an image, but rather a "white-space" on the page.
To bring the page to the very top, double tap the top of the screen, just below the time display. This will make the window essentially scroll all the way up.
Safari Tip #4: Navigating Websites - Scrolling Pages
Safari will hide the scrollbars on a webpage by default. To show them, simply start scrolling using your fingertips. Drag the pages up or down and notice the scrollbar telling you how far down or up you still have to scroll to reach the end.
When you flick up or down, Safari will scroll faster. To stop it at a specific point, just tap the page.
Safari Tip #5: Zooming - Text and Images
This double-tap function is pretty powerful in Safari, and it acts differently depending on which item you apply it to. Double-tapping on an image in Safari will zoom the picture so that it fits your iPhone display. Double tap again and your back to where you started. The same goes for text. Double tapping a text column will zoom and fit the screen. Double tap again and your zoomed out to regular size.
You can also use pinch gestures to zoom in and out anywhere in Safari.
Safari Tip #6: More Search Engines
Fed up with Google and want to use your custom built search engine? That's possible too. Use the Settings for Safari in Settings on your home screen.
Safari Tip #7: More Search Engines
The big news with 3.0 when it came to Safari and images was how you can easily save them on your Camera Roll. Tapping and holding on the image will bring up a screen that lets you copy and save them to your camera roll.
Safari Tip #8: More Domain Extensions
You probably know this already, but to navigate to a .com in Safari, you don't need to end the web address in ".com" as Safari will take care of that. So type out simply "appbite" and it will take you to the Appbite.com homepage. The trick doesn't work when you're trying to get to a domain not ending in ".com".
Fortunately, the Safari keyboard provides you with some nice extensions right out of the box. Instead of typing on ".com" on the keyboard, tap and hold it and it will bring up new domain extensions including ".net" or ".org".
Safari Tip #9: Add Bookmark To Home Screen
I saved my favorite for last. As I have several webpages that I visit daily, I need to keep several windows open in Safari, so I don't type out addresses every time. But there's an alternative to that. You can bookmark a webpage from Safari right on your home screen.
When you're in Safari, tap on the "+" sign and select "Add To Home Screen" to create essentially a bookmark of that webpage on your home screen.
You can even customize the icon that appears on your home screen. This is a bit tricky and it didn't work all the time, I can't really figure out why. When you save a bookmark to the home screen, Safari will essentially take a screenshot of the page and use it as the icon. Sometimes, it picked up on the favicon.ico, sometimes it didn't.
A small workaround to this is to zoom in to a part of the webpage you want to use as an icon, and then hit that "+" sign. I'm still a bit puzzled as to how essentially Safari does the icon, so if you happen to know, share it here.