Alex, I asked myself that question too when I started playing.
A very helpful site for odds
is Wizard of Odds:
If you look at the heads-up odds of hands, you'll see the coin flip again:
These types of tables are created with the math explained on the wikipedia page and the numbers are confirmed with software that runs millions of hands and comes up with the same percentages for these types of tables.
I've used Poker Academy (http://www.poker-academy.com/) to look at hand combos. It runs 50,000 hands to several million and confirms the results of the Wizard of Odds (http://wizardofodds.com/games/texas-hold-em/) tables or hand calculators (http://wizardofodds.com/games/texas-hold-em/calculator/).
Hope that helps a bit.