This is a good game for practice with ordering decimal numbers. You should preview it before you share it with kids, however, as Builder Ted's pants don't fit too well. When I used this with my kids we just talked about whether they could be mature about the British humor, and it wasn't ever a problem. Select Level 1 as 2 and 3 have negative numbers.
This is a great site for modeling perfect squares and other numbers by using arrays. It shows the equations so kids can see that a perfect square only has one while other arrays have two (commutative property).
This site allows kids to explore decimals on a number line, which makes it really easy to show how to round up or down.
Click the hardest level for ordering decimals.
Choose Proper Fractions (Easy) for this skill. The hard version would be a great extension. Both go beyond the benchmark fractions.
Various interactive activities.