Default keys (they're changable) that i personally love:
F11 - "Show desktop" equiv for OS X, but instead all the windows are moved to the sides of the screns for a moment, when you press the key again they return.
I guess it's called Expose or soemthing.
Another.. F10 - All non-minized windows are cascaded *temporarily* and you can easily hover your mouse over each item and see it's name. Click, it becomes the front window and you can move it around as needed.
Another... hold apple (command/windows) key and press the title of a window in the background... you can move the position of a window without changing focus.
they're simple little things, but.. if you want windows-style "fullscreen" you're probably looking for a "maximized" (The box in the middle of the 3 buttons ona PC) equiv. What you can do is shrink your Dock (the Taskbar equiv in windows) in OS X then press the + green button (maximize in OS X) and that is almost identical to maximizing in Windows.
If you're meaning Safari doesn't run "fullscreen" when you're browsing the internet, you can download Firefox and go to View.. Full Screen (I believe?) or another browser.
Also pressing COMMAND+tab will switch apps just like pressing ALT+TAB in windows. Or right click applications on your Dock in OS X, you will get a list of current runnign windows.