Why cant i go beyond level 20??? apart from getting books and bobbleheads, I cant get my skills any higher, and there are some perks I really wanted. I have it on the PS3, and want to get all above 100.

Because Bethesda wants to force you to specialize so that you'll have more replayabillity by trying different kinds of characters that are good at different skills instead of one single character that's good at everything.

Not to mention that a level 20 character is already powerful enough to tackle just about any enemy in the game. Raising your stats even higher would be pointless.

funny that they want you to specialize. Because it doesn't seem that way. Honestly at lvl 20 I have half my skills at 90 or 100 and I'm a god in the wasteland. What happened to the other half of the skills from Fallout 2 and the ability to raise it to 300% and the crippling factor involved in putting skill points into non tag skills...what exactly is the point of tag skills in fallout 3? They watered down a system that did not need to be watered down.

What Beth should have done....and could still do....is to stretch what you can become at lvl 20 out to say level 30 or 40. I want to be able to do all the side quests and NOT reach maximum level in the middle of the game. I haven't even explored 1/4 of the map yet and I am at level 10. Once I reach 20 then that takes away some of that level of accomplishment while I play....which sux.

This is probably the worst mistake bathesda did, even with lvl 20 limit you can almost max everything that you become jack of all trades ,at level 20 i wear power armor and have 100 skill on energy-small g.-sneak-science-repair and pick lock...i have 5 endurance and got 400 hp ,and now you are a god like creature killing everything in 1-2 shot and not earning any xp in return and loosing your interest in the game, this game need `talent trees` ,if you are a strong soldier with power armor training and can use heavy guns perfectly than your sneaking,speaking or science skill must be much much lower or you shouldnt even have the option to get those skills.
But ofcourse in this case you need some other skills like `demolition` to open locked things or `intimidation` to force people to do what you want and vice versa...

And guess what if you cant have some skills when you choose others now you have a reason to play this game with another character, i am forcing myself to play with my second chracter but everything going down to same route again..

i guess you could use the "here and now" perk at lvl. 20 to reach 21.

Nope you cant that perk gray out at 20.