https://github.com/citycoins/citycoin
https://github.com/blockstack/stacks-blockchain/blob/master/src/chainstate/stacks/boot/pox.clar
https://github.com/blockstack/stacks-blockchain/blob/master/src/chainstate/stacks/boot/bns.clar
https://github.com/arkadiko-dao/arkadiko
https://github.com/psq/stacks-open-oracle
https://github.com/friedger/clarity-smart-contracts
https://github.com/friedger/clarity-marketplace
https://github.com/friedger/clarity-friedger-pool
https://github.com/syvita/sypool
https://github.com/syvita/daoos
https://github.com/syvita/nothing
Just to name a few...
And of course there is a search engine for clarity contracts: https://search-clarity.dev/