I just realized that I would like a bookmark indicator -- not a menu, but a stretch of buttons on the indicator taskbar on the top of the Ubuntu desktop that can directly be clicked to call a particular web site in the default browser. Has anyone stumbled across a thing like this? I'm using 12.04 and 13.04 on my computers.
It think it would be possible...
On Ubuntu you can middle click an indicator icon. Your indicator could capture that event and then fire up your browser and open the bookmark (URL) for that icon. In my indicator-fortune I respond to middle mouse clicks show a notification - but you'd do the browser thing.
I'm suggesting the middle mouse button since you said you don't want a menu as such.
Also, your indicator would have to manage bookmarks, so you'd still need a menu to show a bookmark manager - just a list of bookmarks. Or perhaps the indicator simply parses a known .html/.xml file - up to you.
If you wanted to have an icon per bookmark (not very scaleable) then your indicator proper would have to loop over your bookmarks and fire up a separate indicator for each.
I'd suggest a single icon and then list the bookmarks in the menu...you can then also have sub-menus to categorise your bookmarks.