Here's a compelling way to let kids get the difference between tenths and hundredths.
First, get a Nerf basketball and hoop. If you can't do that, put a wastebasket on a desk next to a wall, and crumple up a piece of paper. Tell the kids you are going to pick 10 of them to take 10 shots, based on how well they do (whatever it is you want them to do -- you could drag the selection process out all day. For some kids, especially kinesthetic learners, the opportunity to take even one basketball shot, much less ten, is very strongly motivating, so if you want to use this activity as a reward for their participation in a prior activity, that would be a good way to get them warmed up and ready. You could also pick seven kids ahead of time and leave the last three to be picked based on participation in the actual decimal activity, which I will now describe)
Have kids come up one at a time and take ten shots, from not too far away. You want them to make some shots so it's exciting and rewarding. What you want your whole class to do is write: a) the name of the student taking the shots; b) how many shots out of 10 he or she makes, in word form (for example, Da'Quan -- 6 out of 10 shots.) c) write the shots made as a fraction of shots taken and d) write that fraction as a decimal. This part of the activity will be a lively and memorable way to get your class understanding and repeating the relationship between fractions of 10 and decimal notation.
After all ten kids have take their shots, ask the class to tell you how many shots out of 100 they made. Let students add up all the shots and tell you. Then ask them, how many that total is out of 100. So: if your volunteers made a total of 36 shots, clarify with the class that they made 36 out of 100. Show them that this is written in decimal form as 0.36.
As a follow-up, select ten more kids to take shots, and let the class do more of the work in computing the fractions and decimals. You can keep track of progress on the board in progressive fractions -- for example, if a kid makes the first shot, that's 1/1, misses the next, that's 1/2, makes the next, that's 2/3. If this activity catches on in your class, you could have kids keep track of their data and make graphs. You can also ask the kids to compare their "free-throw" shooting to results by professional basketball players. Bring in a sports page and let them interpret how many free throws the best players make out of every 100 they take.
If you whip out the digital camera, you can put pictures of them shooting hoops along with their graphs and tally sheets to make an admirable bulletin board.
You can also extend this activity to other experiences, such as seeing how many kids in your class can jump rope more than 100 times in a minute. That will show them decimals less than and greater than one. It's also good exercise.