Making your own stationery? I've just come across Liz's Crafts (liz-craft.co.uk), which is perfect for all your crafty supplies. It does everything from card-making kits to insert papers, glitter, rhinestones and more. There's also a dedicated wedding shop with rubber stamps, stickers and motifs for decorating your menus, invitations and table name cards.
And if you're thinking of having DIY favours, check out DIY Favour Boxes (diyfavourboxes.co.uk) which should give you plenty of inspiration. It has mini favour buckets, cute boxes, favour nets plus personalised items, as well as design ideas and tips.
Let me know if you've come across any great DIY websites - I'd love to hear about them.