Encoders and decoders for common data encodings (base64, hex) which avoid branching or performing table lookups based on their inputs (a.k.a. "constant time-ish").
Base64 encoding with (almost) data-independent constant time(-ish) operation.
Bech32 (BIP-173) checksummed Base32 data encoding (WARNING: preview!)
Hex encoding/decoding with data-independent constant time(-ish) operation.