My husband really enjoys giving "Hallmark" cards to special occasions. He spends time going through different card ensuring to pick just the right one. I on the other hand have always preferred the cards that blank on the inside...aka box of 12 for $5.99. Not only is the price more favorable, but I have always enjoyed a more personal way to express my note.
Fast forward to having children, I always have tons of "beautiful" art work hanging around. My oldest daughter loves to paint and draw and play with stickers. I often feel bad about throwing her creations away. Why not share them with someone else. So I have started using her art work as personal handmade cards to share with our friends and family. I typically have her "sign" her name and I write the special note.
Another great tip is to take cards, (the "Hallmark" kind) and cut out the picture on the front or inside pages. We get a lot of great cards with pictures of say Disney characters or flowers, hearts, etc. I cut them out and save them to be used for other fun projects! My eldest daughter loves to glue them on to other pieces of paper for more art creations!!