I haven't read the other responses so forgive me if I repeat anything.
My son had just turned 2 when Abbey was born, and I was a single mom as well, so I was really nervous.
A couple things that I think helped:
Referring to the baby as "our baby" not "my baby" or "the baby". Levi loved telling his friends and family all about HIS baby.
It's hard when you're young seeing everyone making a fuss over the baby ALL THE TIME and giving present after present. Making sure that big brother is presented with something once in a while will help. It doesn't have to be anything huge or expensive. Even a toy from a quarter machine is nice, just a little treat. Also, remind your older child often that when he was a baby, it was the same way. Everyone was excited, he got lots of gifts, etc.
Involve big sibling as much as you can. Let him know you need his help! This makes him feel useful and important. Let him "overhear" you telling others how helpful he is and what a great big brother he is. He will beam with pride.
It's quite the adventure going from 1 kid to 2. Good luck!
