Is there any way to install the Google toolbar for the latest version of Firefox (12.0+)? Recently I have reinstalled Firefox and can't seem to be able to install the Google Toolbar anymore.
Firstly, I would recommend you don't. What specific part of the toolbar do you need? Firefox already has a built-in search box, you can even mimic Google Chrome's address bar searching with addons like Instantfox. There's plenty of translation addons, etc., etc.. Everything Google Toolbar could do, there's an addon that does the same. Using unsupported software is often a bad idea.
If you still want to go through with it... Firefox 10 addon compatibility checking has been disabled for addons for Firefox 4+. In other words, you can install any addon targeted towards Firefox 4+. Unfortunately, Google Toolbar targets Firefox 3.6.
Luckily, there's an addon that specifically disables compatibility checking for all addons. Note many Firefox 3.6 addons are often incompatible with 4+, so YMMV. It is available here.
Your next step would be to find a source for the actual Toolbar addon. Google has discontinued it and is no longer providing it. A quick search turns up a potential resource. This is not recommended, but if you really want or need to, just download the (.xpi) addon and run it.