I don’t normally celebrate, but I did decide to celebrate my 25th anniversary because I thought 25 years not out deserved a bit of recognition http://www.shootuporputup.co.uk/2009/07/happy-belated-d-day/ – there’s some great ideas in the comments for cards.
It’s my 30th anniversary next year, I’ve already started the campaign that I think a diamond ring would be suitable recognition of my diabetic genius. So far success isn’t looking likely!