Every week, I check out Kristina Werner's design blog for great ideas for cardmaking.  She posts two videos a week, on Mondays and Fridays, where she makes a card in real time.  I can't tell you how much I have learned about cardmaking from her videos.  Her ideas are so good and it's very helpful to actually watch the process.  It always used to take me forever to come up with ideas for cards, but now I have lots of examples, from simple to fancy.  You don't need a ton of supplies, either; generally the things you need are cardstock (or a blank card), scraps of leftover patterned paper, either stamps or stickers for the sentiment, and adhesive. 

If you have any interest in cardmaking, be sure to check out her videos, Make a Card Monday and Finally Friday, which you can access from her site and YouTube.  It's great that all of this content is free, too; many crafters and designers charge for this kind of detailed instruction.