My tab key has broken. I'm due to get a replacement, but is there any key combinations I can use in the mean time instead as I'm in the middle of writing a report.
Sorry, I should have specified, that I using word, not any sort of terminal.
If you are using Microsoft Office Word and want to indent rather than insert a horizontal tab character, Ctrl+M works. If you want to insert a horizontal tab, copying and pasting works, otherwise there's the "Alt Code" method as supplied by Patrick.
For indentation there is also a toolbar button on all versions of Word (screenshot 2010):
Use Ctrl+I instead of Tab
If anything after SP (your space bar) breaks, ask about Alt codes.
If your control key breaks, you may have to save up $10 for a new keyboard.
You could use a tool that changes your key bindings (or even hacking at the registry) and change another key (I suggest Caps Lock) to work as a tab. I'd suggest looking at a page on AutoHotKey explaining how to do that (it also has information on how to do it with AutoHotKey; see below); it's too involved to list here.
Another option is AutoHotKey; it's not as efficient as the above method, but AutoHotKey also allows much more advanced changes (binding a key to a key-combo, auto-replacing entered text, launching a specified program with a keyboard shortcut, binding gamepads to mouse & keyboard inputs, etc). You can also turn the change on and off easily, so if you're in a situation, say, where you need your Caps Lock more than your Tab key, you can just close the AutoHotKey script. The script for this would just be:
Just save that as a text file with .ahk extension and double click to run it (after installing AHK, assuming you allowed it to associate with .ahk files). You can even compile it to a standalone (and portable) executable.