I love this Vintage barbie themed 30th birthday party - very girly, very chic and fun. EAT DRINK PRETTY is the blog I found it on, and that link will take you to the rest of the details of it.
Instead of using it as a bachelorette party, you can theme your 30th on the year you were born. Very cute idea! Source: Linen Lace and Love
Pretty rad 80's MTV cake! Source: Blissfully Sweet Cakes by Jacki
Masquerade parties are also a popular 30th birthday theme. I love that cake!
Here's a cute flapper/vintage 20's party: More ideas here: Tip Junkie
Sleek, chic Audrey Hepburn/Little Black Dress 30th party.