note, you can also do one of my absolute favorite safari tricks if you feel it might help you...
when you are in the bookmark area steven11 pointed out, and then select the bookmarks bar on the left, you can click on the little plus sign at the bottom of the window to the right to create a new folder in the right pane. folders on this side act as drop down menus instead of simple links.
so for example, i have a few called "answers", "apple", and "music". and within those i keep my most accessed pages, such as google and merriam-webster under answers, apple.com and mac-forums under apple, and all music guide and minnesota public radio under music. (obviously i have a few more categories and selections under each, but you get the idea.
the other neat feature about these folders is that there is an "open in tabs" selection at the bottom of each button's drop down. so you could make a folder called "start" or "home" or whatever with a few sites you always seem to open first, and if you click the "open in tabs", they will all open at once in their own tabs.
you can also automate this further in the edit bookmarks area, by checking the "auto-click" on the folder you have those "start-up" links in. then you don't even have to open the folder on the bookmark bar, you can just click the button on the bookmark bar to open all links inside in their own tabs.