Cartolina ($1.99 for iPhone)
Cartolina (V. 2.0) comes with 18 free card layouts, plus 9 additional designs that you can buy in-app for $0.99 each. What differentiates this app from the rest in this roundup is that it supports multiple languages, and offers you the option to send your cards to more than one recipient. In addition, it comes with a calendar that syncs with your phone contacts so you won't forget important birthdays - and will have a card to send or post on Facebook, too.
Vintage Birthday Cards ($1.99 for iPhone)
With the Vintage Birthday Cards app, you can select an image from more than 100 different vintage birthday cards, from the Victorian period to Post-War America, that have been restored from a private collection of vintage cards. Using the app is easy; you simply flip through the gallery and download any image you like (no extra fee). Within seconds, you can send cards to your friends and family, or even use the image as a wallpaper for your iPhone. If you want to make vintage Valentines, Easter, Fourth of July, Halloween, Thanksgiving, or Christmas cards, the same developer has apps for that, too. However, you will have to spend $1.99 for each app.
Cards (free for iPhone)
Designed by none other than Apple itself, the Cards app allows you to create a card and then send it electronically (free) or via snail mail. For the latter, postage within the U.S. is $2.99 per card, while international deliveries will cost $4.99. The day the card arrives, you will receive a delivery notification on your iPhone. You can use the mailing addresses directly from your phone contacts, or enter your own. Purchasing is similarly easy; all you have to do is use your Apple ID. The app works for a variety of occasions, including birthdays or even if you just want to say "hi" from abroad. In this case, choose the "Travel" designs, which can even show your location automatically using GPS.
Best Greeting Cards (free for Android)
Whether you're looking to say "Happy Birthday", "I Love You" or "Get Well Soon," this app can help you make a personalized greeting card. The first step is to choose a design. After that, you can add your own text and one of 15 different image effects. The app allows you to send the card via email, MMS (if enabled by your data plan; SMS sends only the text), Facebook or Twitter.
3D Animated Greeting Cards (free for Android)
This Android app comes with a CardzCreator that will allow you to make cards that are not only animated, but that appear in 3D and can be accompanied by music. Essentially, you have two options: to purchase an e-card that is ready to go, or to make your own. If you decide to create your own, you can choose from a series of 3D themes, including chocolate boxes, bouquets of flowers, cakes and more. After that, you can customize the color and/or the background design, in addition to typing in your own text (you also select font sizes and colors). You can preview the card and once you are happy with your creation, send it via email, Facebook, Twitter or MMS (picture message). You can track your cards and chat with your friends within the app. Updates and new cards are frequently available.