Also: Hey Tarah! Just saw this was you. Great job with LadyCoders, I hope it gets even better.
Most of the issues are fairly unconscious bias. Some people just assume women aren't as good at tech jobs as men are. Some people assume pretty women are stupid. Some people are simply uncomfortable around women, so don't put themselves into a position where they will be around them.
Issues with actually getting women into tech jobs range from their manner of speech (for example, raising their voices at the end of sentences) to being overly modest about their job skills.
"I think I would be a great fit for this company?"