Macbook Low System Memory

Hi everybody, I just joined here because I need help with my new Macbook, which I have had for roughly 1 1/2 months. For the past couple of days, my Macbook went from lighting fast and responsive, to lightning fast and responsive...with being very sluggish at random. I have installed maybe 5 programs since purchasing the computer and have pasted links to screenshots of the Activity Monitor when it swings from one large amount of Free RAM to barely any and becomes instantly sluggish as can be. I've shut it down and tried restarting it and haven't had it long, so I'm not sure what to do. The before and after screenshots with the change in Free RAM, which are about 30 seconds apart, is with me doing nothing but browsing the internet. I appreciate any help.
Screen shot 2011-01-21 at 9.08.26 PM | Flickr - Photo Sharing! <--- MAC Info

Screen shot 2011-01-21 at 8.55.43 PM | Flickr - Photo Sharing! <--Super Fast

Screen shot 2011-01-21 at 8.56.38 PM | Flickr - Photo Sharing! <--Super Slow

G'day and welcome to the forums.

For starters how much free space is there on the hard drive?

Do you run a maintenance utility such as Onyx say monthly?

My hard drive is 250 GB and 228 GB are free. I tried running OnyX, or at least what I could figure out, and that hasn't done anything.

It's not a HDD issue. It looks more like you are maxing out your RAM usage. In the slow screenshot you have a lot more applications open and they are using up more of your memory.

Adding more RAM will help alleviate the problem when you have multiple applications running. Either that or don't run multiple applications all at the same time.