How can I switch to Space 1 with the mouse?
The mentioned BetterTouchTool can definitely do it via keyboard shortcuts.

After you install BTT, switch to Normal Mouse tab. There you click on + Add new mouse button and then click 3rd button inside the Click here to select mouse button.

Next, if you already haven't set up keyboard shortcuts to switch directly to a space, just pick any of the three modifier keys (CTRL, Option, Command), click inside the Custom Keyboard Shortcut field and press the key along with number 1, e.g Ctrl-1.



Note: if you have already set up such a shortcut, you have to disable it before trying to enter the shortcut to BTT, because OS X would otherwise capture this event and BTT won't get it.

Now close BTT window and go to System Preferences > Exposé &amp; Spaces > Spaces and select the appropriate modifier from the To switch directly to a space: list:



Now you should be able to switch to Space 1 directly with Middle click.

PS. I should mention that I have Magic Mouse and have BTT set up with three-finger gestures to switch spaces from mouse - very convenient.