I (began to) wrote a delicious API to implement a toy example for adviserl (thus the code is here). More about the toy example in next blog post.
Haven't found anywhere a delicious API library for Erlang ... but haven't really look for it because I wanted to avoid dependency. So I wrote one, organised in 2 parts.

• The first part (deli_api) is able to:
  • connect to the delicious server and retrieve data (posts) using inets http client;
  • convert those data (posts) in Erlang terms using xmerl (discard XML as different delicious API (rss, api, ...) have different format of the same data);
• The second part is a gen_server (deli_posts) which accept those requests:
  • {login, User, Password}, return ok
  • logout, return ok
  • {get_posts, User, [Option]} with Option=no_update, return {ok, [Post], archive|uptodate}

The server will maintain a local cache (a DETS file) and download from delicious server only if needed and requested. The login is only used to retrieve data from delicious server: data put in cache can always be accessed without password.
I may like to use this API in order to write a plugin for SharedCopy: any shared URL could be automatically posted in delicious (seems easy with Yaws but I need a web hosting for that).