The only equipment I have is two 10 kg ( 20 pounds..?) dumbells I use in a bench-press like exersise, and then I do lots’a push-ups in different variations. But none of these exercises seems to do anything to strenghten my pectoral muscles, so does anyone know some other exercises which isolates the pecs, and strengthens them effectively?
if you wanna get a strong chest bench press is the best way to go 
if you can’t get something to do those with or join a gym, i guess you could get someone to sit on your back while you do pushups 
If you only have access to 20 pound dumbbells, I would suggest some dumbbell flies in addition to the bench press. You can also do incline and decline flies. Couple these with pushup variations and a wide grip dumbbell bench and you should have a good enough chest workout.
There´s more to it than bench bress.
-and one exercises is unlikely to be sufficient for the whole chest.
Click&nip from and around this site;
http://www.bodybuilding.com/fun/pecs.htm
This is not directly answering your question but I believe this won´t leave you cold.
Triangle push ups work good for pecs.
(hands in make a diamond shape, put nose in middle)
Try the bench press single handed with your feet in the air. That will work your core stabalization along with your pecs. Do this with the fly as well.
Flat bench and weighted dips are my choice.
thanks for the help. I’ve been thinking about buying a barbell-bar, so i can put the plates from my dumbells on it. It’s just that.. I don’t have enough space in my appartement, and NO BENCH, so how am I gonna do benchpresses? on the floor? that can’t be right.
and Shaolin-do.. I thought triangle pushups only build the triceps, but I guess it’s because I do them above my solar-plexus. I’m gonna try that variation.
Hey dude, benches are CHEAP ! I always thought it was very expensive, but I’m getting one asap when I finish my exams at university, they’re very usefull, very durable, and very cheap ! (I saw a great one, for something like 50 € !) (no weights included, just the bench)
Yeah, but you need the room. I live in an apartment as well and I would love a bench, but there just isn’t the room.
Gawd bless the bodyweight routine! 
If you are serious about benching, you will need a bench that has a rack to hold the barbell. Just a plain bench by itself won’t work… how will you get the barbell in place to start benching? Maybe your partner could deadlift it up and hand it to you, but it’s safer to get a bench that has racks that can hold a barbell.
Good luck,
IronFist
I just don’t have room for it, so I just don’t think it’ll work out:(
i guess I just have to stick with bodyweight-exercises, so can anyone tell me the best ones, or some push-up variation that works the pecs especially?
For a bench, I used to line up chairs.
As for pushups, keep changing your hand position.
Put some weight on your back.
Put your feet up on your couch.
Get a couple of chairs and put your hands on them to push up.
How do you line the chairs up for benchpressing? how are they supposed to stand?
Be careful not to cripple yourself.
You put one chair at the head with the back facing out. The other two chairs are in front of that one, but facing eachother–so that all three seats are touching. You can use more chairs if necessary.
thanks robinF, for the info
i guess the whole idea of the bench is to allow your elbows to move down past your shoulders and back..correct?
Yes, that’s the idea. Putting a chair at your head, schooch up so your shoulder blades are also on that chair and have the other chairs to support the rest of your back if you need them.
Call me Robin.
OK Robinf;)
but the chairs still doesn’t solve the problem with the barbell-rack.
Be careful not to injure yourself.
If you´ll do it,make sure to use low weight.