I have no idea whether this function is common knowledge, but yesterday I discovered that copying the URLs of all open tabs of a window is quite simple in Firefox (3.5).
Select All Bookmarks... and save the tabs into a bookmark folder.
Next, locate the new folder in your bookmarks, right-click and select
The effect is that the clipboard now holds all the URLs contained in the folder.
If you paste as plain text (e.g. Notepad), only the URLs will show. If you paste as rich text (Word, Outlook), you get hyperlinks.
Searching the intertubes brings up a lot of add-ons that might save you a click or two, but its good to know that the function is essentially built-in.