I've been using Gmail's labels for a very simple database. I email myself contact information (address, phone number, email address) for my friends, using the person's name as the subject line. Then I label the email with
contact. When I want to look up the person's contact information, I can search name label:contact.
This also works for recipes. Email yourself each recipe as a separate email message, using the name of the dish as the subject line. Then label them with
recipe. When you want to find a recipe in your database, search for dish/ingredients label:recipe.
What are other ways to use gmail as a lightweight database?