Well I must disagree with the poster who said it goes away with age. I mean, the physical part of bullying certainly goes away, but people tend to push around and use others they perceive as weaker than them (mentally/emotionally weaker). Even for people who are big, they can still be bullied in this way.
That is why you have to stand up for yourself now and tell them to stop. You might get the crap beaten out of you, but you can’t show any fear and never back down.
You have to be confident in yourself. The more you (not “you” you but as in people in general) let people push you around now, the more you will continue to let them later in life.
I tried the “ingore them” route and while it works for adults it didn’t work when I was in school. So… I learned the above lessons the hard way.
If you are in school, the only thing is, make sure you don’t START a fight (or say “let’s fight” or anything), because nowdays in school you will be the one who gets in trouble not them. Some schools expel students over one incident now, even though obviously those guys are the problem not you, so just be careful.