Using Right Ctrl for Ctrl+L is extremely useful for me when browsing. I miss it when I use my HHKB.
Right Alt is probably more important for non-North American folks for AltGr. For me on the other hand, I re-program (or when I can't, registry re-map) it to Caps Lock, and have Caps Lock be Left Ctrl.
i remap right alt to ctrl.
press right 'alt' + l to focus on browser address bar
Ctrl+L to go to the address bar? Alt+D does the same thing (at least in windows).
Added benefit, it does the same thing in a windows explorer window so you only have to remember the one shortcut.
All the shortcuts that everyone uses with the right modifiers, I just use the left modifiers and two hands. I don't find that I'm doing anything that requires those type of shortcuts unless I'm pretty into what I'm doing (Coding, Word, Excel, Photo Editing, etc) and in those cases both my hands are right there anyway because I'm working. Plus, I'm left handed and using my right hand for those tasks feels completely unnatural. I'd prefer if every keyboard removed them and stuck dedicated arrow keys there. I'd actually use those.
I know of one program that I use that by defaults uses the Right Ctrl, VirtualBox. It uses it to exit from the auto capture keyboard/mouse. However, you can change it in the preferences. Out of pure laziness I haven't changed it and every time I have to exit from VirtualBox back to my Desktop it takes me like 15 seconds to think about what I'm about to do and it feels "yucky" doing it.