I was going to start a new playthrough of Arena and Daggerfall and was wondering what mods, if any, were available for them and worth getting. Any suggestions would be greatly appreciated. Thanks!!

No real mods for those games. No editors to make them with is the main reason. About the only thing you are going to find are Patches and Save Editors

http://www.uesp.net/wiki/Daggerfall:Files

http://www.uesp.net/wiki/Arena:Files