Is there a program for Mac that tells me whats eating my memory?

Do you mean RAM or hard disk space? For Disk space i would try Disk Inventory X

Disk space.

Also check out Activity Monitor, it’s already built into your OS! It has many nifty ways to monitor things like memory, Internet activity, CPU usage, as well diskspace usage.
Good luck!

Activity Monitor is good too, but if you want a visual representation, I would try Disk Inventory X. It may take a while, but I think it’s a pretty good app.

Disk Inventory X is an EXCELLENT program as @dverhey pointed out

iStat Pro from iSlayer also does a great job when it comes to clearly showing what’s eating up your RAM.

for disk space i always use grand perspective, seems it works about the same as DIX