The actual maximum level is 81.
Level 1-50 is what people call the 'softcap', this means from level 50 and onward it gets progressively harder to level until level 81.
'At higher levels, leveling up happens much more slowly, however there is no discrete change upon reaching level 50. Level increases in Skyrim follow a formula. The maximum level is level 81 and is reached by increasing all skills to 100. With every skill mastered, the level progress meter will rest a little over halfway to '82', meaning it is not necessary to master every skill to achieve Level 81.
One implication of the leveling system is that although it is possible to create a character with 100 in all skills, it is not possible for one character to unlock all skill perks, unless a console command is used (player.addperk). In such a case, one may unlock every perk available, even at level 1. There are 251 total skill perks (including multi-point perks), but only around 80 of them can be unlocked by any given character.'
Text from Skyrim Wiki
As you probably read, you have to level every skill to 100 to achieve the maximum level basically.
Here are pictures also,
http://i40.tinypic.com/71rybd.png
http://i39.tinypic.com/mkdn9.png
You can gain 80 skill perks in total, and there are 251 different perks to chose from, so you better pick wisely.
I probably know most of you already have heard about this, but there's still the small majority of people that don't know and make the occasional thread about it.
So I hope this made it clearer.