These invitations I found on Flikr are pretty cool. It looks like they made the Lego portion out of construction paper and glued a store bough invite to the inside.
And this is a cute idea from Launder, Fold, Repeat.
I found these decorations on Pinterest. It would be easy to create your own by printing out the heads and stringing them up with ribbon.
These plates are from Delia Creates. It is a simple and effective idea to buy the square paper plates in yellow and draw Lego faces on them. I love the added detail of the paper on top just like a real Lego man. Make sure to check out her site, she has many more cool lego party ideas!
This utensil holder, shared by Rindy Mae is perfect! So easy to construct that your birthday child can do it themselves in preparation.
This idea from Simply Sara to put a few Lego pieces in your soap is a neat way to surprise guests when they use the bathroom (and hopefully encourage the kids to wash their hands)
These juice boxes and straw decorations came from My Many Colored Days and are brilliant! While you are checking those out, make sure you read some of her Lego themed activities and check out her favor bags, pretty awesome stuff!
These Lego head cupcakes are from Mama Dani's Musings. If you can't find yellow Marshmallows there is also a tutorial on how to make your own at The Boxed Party Company.
Lego Cheese and crackers make a great appetizer! These are from Kiwi at Heart.
Pizza is one of the best things to turn into Legos. This idea comes from Take Me To Your Latte.
Another great find from Rindy Mae were these adorable Lego brownies!
These Lego Head buckets can be used to hold food for the party, and then storage for your child's Legos after! Check out obSUESSed for the "how to".
These Lego food cups from Boys' Germs are a great way to sneak in a little health food for the kids :)
When the kids come in you can have them each write down their guess and the closest gets a prize! Great idea from Crunchy Catholic Mamma.
This pin the head on the Lego man game is from Production, not Reproduction and is very easy to DIY.
I love this idea of the kids creating their own personalized Lego men from Catch My Party! If you just Google Lego coloring pages you can find a bunch of cool printables for free.
I think this is my favorite Lego party activity. The kids all build their own cars out of Legos and race them down a homemade ramp. I found this awesome idea on a blog called The Painter Family.
This is a pretty sweet board game. Each Player picks out their Lego person and at the end of the game, whoever has the tallest tower wins. Christiansen Chronicles was nice enough to share not only the idea, but also a printable!
These are a totally fun and cute idea from The Centsible Life. You could even make them into sort of charm bracelets because you can switch out different Lego pieces to fit on top.
I found these nifty bags on Pinterest and they would be just perfect for Lego Party favor bags!
This cute hair clip is from Etsy, but I bet you could make your own as well.
These baby food jars turned Lego containers from Baby Center are another great favor idea!
Thank you notes:
These thank you notes from The Custom Invitation made me giggle (I am a sucker for puns when it comes to kids' stuff).
Party on, Legomaniacs!