Are there any side effects of Installing and uninstalling lots of apps on an Android smart phone?
Specifically are there any things that do not get cleaned up that I need to be aware off?
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.
Aside from SD card, if the application connects to a server to provides its service, it may stores data in the server.