Great little tool to help learn the importance of good vertical rhythm:
I’ll add to this as I find more but these are a pretty good starting point…
Isobar – http://na.isobar.com/standards/ via @paul_irish
Page Up People (Mark Brown) – http://yellowshoe.com.au/standards/
Do yourself a favour and start using it. You can thank me, and more importantly the guys & gals behind it later.