When you open a folder in the Finder you should be able to scroll through your documents in the Finder with no problem; however, there may be an issue where when scrolling through your documents the scrolling behavior is jerky and choppy. This may be due to several reasons, including disk usage, and corruption in DS_Store files or caches, all which may interfere with the icon loading behavior of the Finder.
If the system is using the disk for other purposes (ie, spotlight indexing) then this process may take a little time and scrolling may be jerky as a result. Usually it is expected for icons and previews to load slower when the disk is in use; however, sometimes processes like "mds" for spotlight indexing will take off with disk usage and cause slowdowns. Usually a simple restart can clear these problems, but periodically a forced quit of the wayward process using Activity Monitor may be required.
An additional reason why the system may be slow at loading icons, or at any other task, is if your hard drive is nearly full. A full hard drive will cause the system to run low on virtual memory space and have problems managing memory. This will make it use the disk more than it should, and result in poor loading behaviors. Likewise, if you are low on RAM the system will spend a lot of time writing the unused contents of RAM to disk, which also may result in poor system performance. You can check the RAM and disk usage in Activity Monitor.
The Finder will cache image previews once they are loaded, so while you may normally experience a chop or two when first scrolling through a folder, things should be smooth once they're loaded. If not, then there may be a problem with how the system has cached the images or how the system is handling the folder views through the .DS_Store files, the later of which may be the case if only certain folders are choppy.
To clear the icon caches, try booting into Safe Mode and restarting again, and also run a system maintenance utility such as OnyX, Cocktail, or [Snow] Leopard Cache Cleaner and clear user and system caches. Then reboot the system and the loading behaviors should be smoother. Running a permissions fix with Disk Utility while in Safe Mode may also help.
DS_Store files require a few more steps to remove manually, but there are a number of utilities (including OnyX) that will remove them from specific directories or directory trees, or from the system as a whole. You can do this on a per-directory basis from the Terminal, by entering the following command sequence:
Open Terminal and type "rm" followed by a space.
Drag the folder that has choppy behavior to the terminal window.
Press the delete key once to remove the trailing space, and complete the file path with "/.DS_Store"
With the command looking similar to the following, press enter.
This will remove the DS_Store file from the system. Unfortunately, DS_Store files can be difficult to troubleshoot because their behaviors are inherited from the first opened window, so you may need to figure out which folder was opened first (likely your home folder, or the root of the hard drive) and remove the DS_Store file from there.