I've been loving yellow lately.  Here is a cute birthday party from one of my favorite blogs, 
Hostess with the Mostest.  The cool thing is that you don't have to use it just for a baby's birthday party, but you can adapt the idea for other events as well. 

Buy a cheap frame from a thrift store and spray paint it.  Easy!  They sell letters at craft stores for a couple bucks. 



Use scrap fabric from old t-shirts or sewing projects.  Again, so simple!