Most insurers will do this. I've gotten insured on my dad's car a few times for a week / two weeks. If you ring them up they should be able to sort it out.
Although Aviva (Ireland) seem to have some rule where you can only add somebody short term 2 times a year, or no more than a total of 30 days, whichever comes first. I've already been added twice which leaves me in a pickle as I need to be put on the insurance this summer for driving on holidays (myself and my dad usually share the driving).
Edit: This was on somebody else's policy, which is not what you are looking for OP, so I'm not sure! I've heard of people getting added for a day because of driving tests, etc. , but usually that's as a named driver.
Last edited by **Timbuk2**; 29-05-2011 at 11:27.