If you have to fly with it, or you don't have a huge car boot, I second the idea of getting a "tent" kind of one, like the Phil and Teds, or the Kindercot.

We have the Littlelife Arc 2 portable cot. It works like a tent, seems very stable, so I don't think a toddler could tip it over. It's working a dream currently, as we're travelling overseas, and of course we could manage it in our luggage for overseas, which we certainly couldn;t have done with a conventional cot.

One thing you need to know about the portable cots like this is that there is a problem, in my opinion, with many of them, which is that for safety the mattress can't be put inside the cot. They are designed to go into a pocket underneath. This means that you can't put a sheet under the baby. Which, if you have a spewy baby like outs, is a real problem.

I chose the Littlelife one specifically because it does have an internal mattress, which velcros down securely to the base, and therefore it comes with a sheet, which fits tightly around the mattress. I wouldn't say the sheet is as well-secured as a tight fitting sheet on a normal thick mattress, but it seems to work fine for DD at this age, anyway (and she's very wriggly and rolling in bed at the moment, so she's pretty much all over the cot).

I bought mind from a UK-based website, with free postage, for around $100. Frankly i was amazed at the price, and I'm very happy with the cot.