How Do You Organize Your Data?

kpellegr asks: "After returning from a well deserved holiday, I was faced with an exploding inbox. While organizing and deleting my mail, I realised I was having trouble classifying each mail into one specific folder. I had the feeling I should be able to link to one email from several folders (e.g. product information should be linked to from the 'vendor' folder, as well as from a specific project folder where this product is used). The more I thought about this, the more I realised that trees (such as the Windows filesystems) are not really ideally suited for organizing data. On UNIX-like filesystems, symbolic links allow the creation of simple graphs for organising data, but I have the feeling data could be organized more efficiently. How does the Slashdot crowd organize their data? How do you manage files, email, contacts, meetings and all the relationships that might exist between them?"