Delicious is used a lot for recipes, if they're online. You can make a tag group and use it with your current delicious account as well.

I've been on-off using springpad for the past three months and I really do like it. (http://springpadit.com/springpad/#apps/app/recipebox) I'm about to sort out my Lent mealplan on it, and the nice thing is that it's easy to follow the receipes and shopping lists on my iphone.

I went through a bunch of online apps for mealplanning, but most of them were proprietary. Springpad allows more flexibility.