Activity Monitor reveals that...

[macswitcha2]

all 4GB of RAM (memory) on my late 2009 27" iMac is being used but I only mail, Safari, iTunes, VLC, and MoneyWell running. I know shutting these apps can free of RA< but that seems like small tasks for using up all my RAM.

Is there anything else I can do to free up RAM and get my machine to function better?

 

[DeltaMac]

Yes, you have memory, and it should be used.
Free memory is wasted memory.

However, are you actually having performance issues now? (system much slower than you expect)
If you are running Mavericks, you would commonly see all memory is in use. The Activity Monitor will tell you about memory pressure. Another item in that memory tab is memory page outs. Lots of page outs can indicate that more RAM installed might improve your system, and could bring it back up to speed.
And - your iMac can upgrade up to as much as 32 GB…. but doubling to 8 GB may be a good plan, assuming that you are getting page outs, or the memory pressure reported in Activity Monitor is high.

 

[Cubytus]

Yes, you have memory, and it should be used.
Free memory is wasted memory.

Disagree. Free memory is swap memory that doesn't get used.

This was a significant problem 15 years ago with much slower HDD and much lighter applications, and it is still an issue nowadays with glutton apps, even with a fast SSD to hold swap. Constant reliance on swap is what causes so many powerful machines to feel sluggish.

 

[Apple fanboy]

all 4GB of RAM (memory) on my late 2009 27" iMac is being used but I only mail, Safari, iTunes, VLC, and MoneyWell running. I know shutting these apps can free of RA< but that seems like small tasks for using up all my RAM.

Is there anything else I can do to free up RAM and get my machine to function better?

You also had OSX running. That will take up RAM as well. Can't you increase to 8GB? RAM is cheap and easy to install on your iMac.

 

[RedCroissant]

all 4GB of RAM (memory) on my late 2009 27" iMac is being used but I only mail, Safari, iTunes, VLC, and MoneyWell running. I know shutting these apps can free of RA< but that seems like small tasks for using up all my RAM.

Is there anything else I can do to free up RAM and get my machine to function better?

Which OS are you running? If you upgraded to Mavericks, then 4GB will not be enough.

And there were 4 late 2009 27" iMacs. Which one do you have? The C2D versions of the Late 2009 can use 16GB of RAM and the i5 and i7 versions can use 32GB (according to EveryMac.com and OWC).

My advice if you're running OS X 10.8 or higher is to max out the RAM. You might not need it now, but this will save you money over upgrading again at a later point.