One really different one that I did for mine was I put on the invitation for everyone to bring a baby photo of themselves. You can call them since it's close. I bought a huge poster board and drew flowes and such on it. When the guests arrived, my sister put them on the poster board with double sided tape and silly saying stickers captions coming out of their mouths (be careful not to put stickers on the photos...some of mine stuck to their photos) and then she numbered them.
We put the poster board where everyone could see it and had them guess which guest matched which baby. It made for conversation and mingling of families...which I needed at mine.
Also, a fun one is to have ten diapers with melted and mashed candy bars. They get to smell the diaper and guess what candy bar it is. I like it better than the baby food one.
For thank you cards, have each person self address a blank thank you card envelope and drop it into a bowl. Draw a name and give a prize. Now you don't have to address your thank you cards later and you have a complete record of who came so you dont' miss anyone.
I also did a timer while I opened gifts. My sister would set a timer to go off every few minutes (depending on the amount of gifts you have to space it out and how long it takes to open them)...the timer would go off and whoever's gift I was opening got a gift too. I did a lottery ticket taped to a raspberry chocolate truffle from See's Candy Story. Makes gift time fun for them.
My friend bought cheapy bibs and markers and everyone drew on them during the party. Some came out very cute.
Nursery Rhyme game is fun too.
Diaper Doo (Materials-small pieces of white material that can be folded into small diaper lapels, safety pins, one brown crayon). As guests arrive, pin a small diaper to each on their lapel. Tell them they will be told later what it's about. At the end of the party ask everyone to remove their diaper and open them up. One person should have a "special surprise" inside. They win a prize.