Martha Stewart has oodles of DIY wedding ideas. Here's a link that might give you some ideas:
My husband and I also printed our own invitations using our home printer and paper from this store:
They have a ton of colors, shapes, and different embellishments that you can combine to get some really unique designs.
I don't have any DIY ideas for save the dates, but do have a recommendation for inexpensive (relatively) professionally printed STDs and wedding invitations - used an online printer called Birchcraft/Media Plus (web:http://yourinvitationplace.com/Catalog.aspx?Theme=Value&WebName=mediaplus)for both daughters' wedding invitations and STD cards. Their prices were great and they did a nice job.
Click on each tool to see a sample.