From EVEDev

[edit] EVE-Central APIs

EVE-Central.com has several APIs, feeds, and dumps for querying contributed market orders. Note that this is not live and 100% accurate data, as it is provided by users using a market exporter utility.

Included in the data is:

1. Currently active market orders query (XML via HTTP GET)
2. SMTP based feeds for all market orders contributed (CSV via SMTP)
3. Aggregate information queries used by several utility, such as EveMon (XML via HTTP GET)
4. Nightly database dumps (gziped CSV via HTTP)