I've just started a to work out a bit, and the thing I want to concentrate the msot on is my chest, because it's what's least developed...

I found a video on youtube that told me to to push-ups on two benches to develop my pecs (i'm not planning on spending a lot of money on equipment any time soon, so i'm using two chairs)

now i'm already noticing the difference after a few days, but i've notices that the side of my pecs is developing more than the middle...and i'm a bit afraid of doing something wrong so i get a real 'pit' in my chest...

What are some good (and preferably cheap) exercises to work on the middle of the pecs ?

thanks!