I’d like to read / contribute to existing contract standards on Tezos, is there an open source movement like ERC?
Martin Pospěch drafted an Tezos "ICO token" standard at https://gitlab.com/tips2/TIPs/blob/master/TIPS/tip-7.md
Stephen Andrews is working on a tztoken at http://tztoken.teztech.io/
OcamlPro has a token contact (in Liquidity) in its examples available at http://www.liquidity-lang.org/edit/. You can also see code for that at https://github.com/OCamlPro/liquidity/blob/next/tests/others/token.liq
There are currently two standards (I've included permalinks in case things change).
FA1.2 is a simple ERC20 like contract for fungible assets. It does not define a metadata protocol for things like symbol, name or decimals.
FA2 is a multi asset contract. It can hold a single or multiple fungible and non-fungible tokens in a single contract. It also supports custom approval schemas and extensive metadata options.