The Meluna looks interesting, I need to replace my mooncup.
I've been dying to tell someone this story and I think MN is the only place that will appreciate it...
Was driving down to France last week and as is typical with me I came on the day before. A few hours driving in France and time for a toilet stop, obviously also time to empty my mooncup. I was quite heavy so it was a bit messy... and slippery... and I dropped it down the toilet 
Not only did I drop it down the toilet but as I turned to see if it was retreivable I set off the automatic flush 
And that was it, the mooncup gone, never to be seen again. Unless it blocked the system and was fished out by a bemused French plumber!
Must admit that I was giggling to myself for ages as it's such a ridiculous thing to happen.
So... tell me more about the MeLuna... how do you know what size you need and why buy more than one?