1. Pumpkin Math Match:
I found these foam pumpkins at a local craft store. The orange pumpkins have musical math equations on them and the yellow pumpkins have numerical values on them. Students need to add up the number of beats on the orange pumpkins and match them with the correct yellow pumpkin. I include an answer key for them to check their answers to see if they were correct. I also include a sheet that reminds them of the note and rest values as well.
2. Rhythm Jenga
I found this idea on Pinterest. I took a Jenga game and stuck address labels with rhythms on them. Students play it like Jenga, but before they stack it they must say the rhythm.
NOTE: I know this doesn't have a musical math element to it, but I wanted a center or two where they are actually practicing rhythms. Which also gives them a brain break from the math equations.
3. Teacher Center:
I have this center where students come to me to do a small informal assessment. On the paws I have written notes and rests (quarter note, quarter rest, pair of eighth notes, 4 sixteenth notes, half note, half rest, whole note, and whole rest). I randomly draw two to have the students add up the beats for the two. They draw each note in a provided blank on the paper, and then write the answer. 
Another great Pinterest find! It comes from the mastermind of Steph at "Stay Tuned!" My students have LOVED this game. It has inspired me to create other forms of Busted! to practice pitch names as well. With this one, students use it to practicing saying rhythms. But this round, I am asking students to also declare to the group how many beats each stick has on it.
5. SmartBoard: Music Madness!
I don't know about the rest of you, BUT I LOVE Artie Almeida's resources. Last year I bought her Music Madness Interactive Board games. And my students have LOVED it. I am having them use the game "An Apple A Day" which is a game where they need to know note values to play, again having them practice their music math skills.
6. Fishing For Rhythms:
I got these cute fish from Lakeshore Learning that is probably supposed to be used for calendar dates or something like that. BUT, of course as music teachers, we get creative and see it as a tool for something else! I wrote notes and rests on them again. Each student takes a turn and "fishes" for 2-5 fish, line them up and they race to write down the correct answer. If they get the answer right first, they get a point. I have them use whiteboards to write their answer. They keep track of their points here as well by squaring off a part of the whiteboard and doing tally marks. Like the Pumpkin Rhythms, I included a note and rest values sheet to help them do the math quickly if needed.Here's some logistics on how I run the centers:
I see students 30 minutes each time, I have students spend 10-12 minutes at each center, which allows me for 2 centers a day. Which then takes a total of 3 days to complete. It takes about a week to get each student through, but I love doing centers because I feel many students learn by doing. So I see a lot of value of doing a centers-based approach. I also love including a teacher center so that I can do a quick review with students who are struggling and challenge the students more who need the extra challenge.
