Are there any side effects of uninstalling Apps
Shouldn't be any major side effects. Most applications are pretty good about cleaning themselves up.

However, a lot of times you will see a directory at the root of your SD card from an uninstalled app. This directory was most likely created by the app to store some type of data externally, whether it be downloads, backups, etc. You may have to manually delete these if they show up. Use a file manager to browse your SD card every once in a while.