for grad schools, you definitely need a 3.0+ GPA to have a decent shot of being accepted.
for engineering majors, it's VERY important (NOT minimal) to have a 3.0+ GPA on your resume, as otherwise you wont even be called in for an interview. they have cut-offs. this is obviously true for your first job attempt.
for instance, IBM only looks at 3.4+ resumes.
unless of course you are very active and have been doing inernships and get offers before graduation. which happens a lot, actually. because in practical work life, your GPA is irrelevant, how you perform projects and deal with your co-workers is far more important.
after you get the first job though, nobody gives a shit for subsequent job interviews. your first job experience takes over everything else.
edit:
Are grad schools like college, where they care about extracurricular activities a lot? Or is it pretty much GPA?
GPA.
professor recommendations.
GRE score.
personal statement.
depending on your major you have to submit portfolios (architecture).