A formal do and nothing to do to that bob?
Here are a few ideas that may work great for you!
Tie a braid the 'french plait' way leaving the fringes loose. Style the fringe with slight rough waves and hairspray the entire section for it to stay like Kate Mara's.
Waves tousled mid-way like Naomi Watts at this Red Carpet looks rather chic and trendy. Perfect for a more semi-formal evening!
Side Swept Curls
Slightly undone side swept curls like Natalie Portman's here can add a dash of style to your lob/bob.
Or you can also go for the specific side swept curls like Dianna Agron's here.
Side Swept Bob
Jennifer Lawrence's Side Swept Bob can make for quite the Retro Hollywood-isque look.
Straight, curls or waves... all you need is a hair styler, hairspray and you're good to go! So what's going to be your bob hairdo this evening?