There is also a fruit called rambutan that is very similar to lychee/longan. I was actually able to buy some last summer at a local supermarket. I recall that when I was looking into them last summer, I read that some species take a long time (e.g. 20-25 years) before they'll bear fruit. Other species bear fruit much, much earlier. So, if you're looking into getting some, read up a bit first. I'm not 100% sure, so don't quote me on it...but it is something to look out for.
Jim
PS the rambutan were every bit as tasty as the lychee I've had, and they have the added benefit of being grotesquely freakish looking on the outside, as well as looking like an eyeball once you peel them. Great fruit for Halloween!!