(5/18/13):
Amazon has put together a page to help when you are planning your next kid birthday party. You can decide if you want to share information about your child with Amazon and create gift lists to share with family and friends. I did not do this. I browsed through the other options.
There is a link for you to be able to find various Theme Decorations
(think cups, plates, cake toppers, balloons or pinatas) by favorite character or theme.
Even if you are not the one planning the party, I liked the Birthday Gift Finder for Kids
to search for gift ideas. You choose the child's age, interest (arts & crafts, building toys, games, sports & outdoor play and more) and the price range that you would like to spend. Once you enter your gift parameters, Amazon will take you to a series of results.
In my opinion the results are far from perfect (for instance, try a search for arts & crafts, ages birth to 24 months, under $25. The suggestion of a leathercraft stamp tool is not a great choice). But we do like games, so being able to browse through games for a specific age group I found helpful. I also liked being able to see which outdoor toys were available for different ages. Yay summer!
Even if you don't want to use one of Amazon's suggestions, just browsing through the options for birthday themes or the gift finder may help give you ideas. Enjoy your parties!
Prices change all of the time.
Double check the price before making a purchasing decision.