The Spinning Beachball

I'm running 10.7.5 on a 2 year-old 13-inch MacBookPro with 8 GB of memory and AppleCare. For some time now I've been getting the spinning beachball cropping up out of nowhere, sometimes when I'm in my Address Book or working in iCal or who-knows-when. It's getting to the maddening stage and happens 3 to 4 times a day. I run Disk Utility and "Repair Permissions" about 3 times a day but it still keeps happening.

What can I do other than take it to an Apple Store for service? The nearest Apple Store to me is a 45-minute drive, and I'd probably have to leave it there.

Thanks in advance for your help.

What size and how much free space on your drive?

Have you installed and run Onyx? Make sure you get the one for your version of OS X - link.
Automation tab - check everything under Cleaning and Maintenance.

Have you run Verify or Repair Disk on the drive?

Beachball

What size and how much free space on your drive?
250GB with 171GB available

Have you installed and run Onyx? Make sure you get the one for your version of OS X - link.
No. I'll give that a shot.

Automation tab - check everything under Cleaning and Maintenance.
Will do.

Have you run Verify or Repair Disk on the drive?
No

This will help with Onyx. As Staff bobtomay suggests next step if no improvement maybe verifying the hard drive:-

Onyx Mac – Instant Download Onyx for Mac OS X » Blog Archive » How to use OnyX for Mac