Bob The Builder Party?

http://www.birthdaypartyideas.com look under construction parties....they havr tons of ideas. hope this helps

Some of the things I did were: get some construction tape...the yellow construction zone tape....and use it as streamer and put on your front door. Get toy hard hats for all the kids invited. I had the kids bring their construction toys..(put names on them!!!) and I used about a bag of dry beans for each kid to play construction with. (inside party...it was January). All the while we had a BTB dvd playing in background. They seemed to have alot of fun.

See if you can find small dump trucks at the dollar store. We used to eat in a restaurant where the kids meals were served in a dump truck or fire truck that they could take home. You could possibly feed them pj&j using the dump truck as the 'plate'.

the food in the dump trucks is a great idea. you could make brownies and serve them in a big yellow dump truck. serve chips in sand buckets. if youre serving lunch...you could make sack lunches with brown paper bags and decorate with bob stickers and give them to the kids on their "lunch break". use plastic construction hats as party hats....theyre about 4 dollars a dozen at orientaltrading.com
make some orange and yellow signs out of constuction paper that says stuff like "party zone" and "birthday construction zone". and if you could borrow some orange cones that would look cool.
for aan activity you could get a big appliance box for free at an appliance store and let the kids paint it with washable paint...tell them its a house!.....you could also give them toy hammers too. i heard you can get free kids tool aprons at home depot. you could write the kids names on them and give as favors. you could also print off some bob color sheets for the kids. hope this helps!