There's a neat trick that you can use to open everything inside a bookmarks folder in Safari at once. Haven't used folders with your bookmarks before? Let's go over that first. So open Safari, and then click on the "Show all bookmarks" button in the toolbar (or press Option-Command-B).
Once you're there, you can click on the collections in the left-hand list to view what you've got in each one.
"Bookmarks Bar" refers to the links that appear in your toolbar near the top of Safari's window. Unsurprisingly, the Bookmarks Menu collection lists what you've got stored under the bookmarks menu at the top of your screen:
What the History collection contains is probably self-explanatory, even if your personal Web history is anything but.
For the purposes of this tip, we're going to be using the Bookmarks Bar collection, so select that. Then you can create new folders to plop your links into by clicking the plus button at the bottom of that window or by pressing Shift-Command-N.
Afterward, drag things around, put your bookmarks into your new folders, and organize your data any way you like. You can also move links out of your Bookmarks Bar from here and put them under the Bookmarks Menu collection instead, which is a good thing to do if you've got tons of links and you don't visit some of them as often as others.
In any case, the folders you put into your Bookmarks Bar collection will show a small checkbox next to them, labeled "Auto-Click."
Here's how this feature works. With Auto-Click turned off, Command-clicking a folder in your Bookmarks Bar will open every link inside it in its own tab. You can tell if a folder is configured in this default way by looking at the little icon next to it. If it's an arrow, you have to Command-click it to open everything in tabs.
However, if you turn on the Auto-Click option shown above, the little arrow will change to a dot, and simply clicking the folder will open every bookmark within it in tabs:
Of course, you can turn off the Auto-Click feature at any point, but if you'd just like to revert to the default behavior temporarily, you can Command-click your configured folder. That'll bring up its usual list of bookmarks for you to pick from instead.
So if you have quite a few pages that you visit frequently, turning on Auto-Click is a great way to bring 'em all up at once without having to open sites one at a time. Keep in mind one important caveat, though—opening everything within a folder (whether using Auto-Click or Command-click) will replace all of the tabs in your current window. So if you want to keep what you've got, it's a great idea to press Command-N (File> New Window) first.
And by the way, if playing around with this feature opened 75,831 Safari tabs for you, here's a fast way to close them. If you hold down the Option key as you close a tab, it'll close every tab except the one you've selected.
So that's two tips for the price of one! Well, they were free to begin with, so I'm not sure how much you've gained. I'm going to pretend it's a lot just to make myself feel good, though.