Well I guess that your traffic is related to your rankings, check if your rankings dropped, if so, did you make any link building activity that could have caused this?
But, no, in general after May 31 I didn't notice any drops in traffic.
There are many many different web design portfolio websites out there.
Two I like the style of:
Bozboz - web design Brighton
Pod1 - digital marketing agency
For more ideas: visit this smashing magazine post.