Math-aids provides decimal worksheet templates at the click of a button with all types of operations.
Common Core Sheets also has all types of worksheets involving decimals, including operations and even number line comparison worksheets.
IXL has numerous online practice for all levels of decimal learners.
Internet4Classroom provides online practice from converting, to operations, and even comparing decimals.
Math-Play is a great resource for many types of games to help with decimal skill building.
Games4Gains has an activity for rounding decimals.
Games4Gains has another for place value
Snaps4fourth has a whiteboard activity which the students always enjoy
TeachersPayTeachers has a multiplying decimals activity that could easily be altered to suit other operations.