I'm going to start this thread as a precursor for additions to the official website section.

Monero tools

These tools can be used to gain information about the Monero network or your transaction data in the blockchain.

Developer tools (?)

Submit hash of file to blockchain. Could be used similar to blocksign or proof of existence if anyone hosts it

https://github.com/ShenNoether/MiniNero/blob/master/MoneroProof.py

PHP Payment thing

https://bitcointalk.org/index.php?topic=583449.msg11108919#msg11108919

python-json-rpc examples

random information

Some question for the devs: What hash functions does Monero use for computing tx ids and key images?

The txids use keccak. The key images computed by hashing the tx public key using keccak to get a curve point*, then multiplying by the private key.

Using some crypto that is beyond my comprehension. See ge_fromfe_frombytes_vartime in crypto-ops.c

Thanks! You are referring to plain Keccak and not CryptoNight, right?

Yes cn_fast_hash which calls keccak1600. CryptoNight is cn_slow_hash

Thanks. BTW, hash length seems to be 256 bits for both.