As seen on the Site Directory and on the respective sites, here are:
The icons for Physics, e.g.:
The icons for Parenting, e.g.:
I know that Physics had its own custom logo for a short time, and will someday get a replacement. And I know that Parenting is likely to launch later this year, at which point it will get its own logo.
But for right now, it's confusing—and that's not even taking into account that (theoretically) Philosophy could go into beta.
Could these be made unique in some fashion?