This page contains links to useful resources for writers. These are
intended for UK-based writers - if you're not from the UK I'm sure the same
type of resources will exist in your country if you just go looking.
ALCS - Author Licensing and Collecting Society
This organisation collects royalties for writers on ISBN and ISSN publications
(printed versions only). If you have a piece appear in such a publication, and
it is over 250 words, then you are entitled to a share. Register here.
DACS - Design and Artists Copyright Society
This organisation does much the same as the ALCS, but for photographs and
artwork. If a photograph of yours is used in a print publication (ie a
photograph you took and therefore have the rights to), you can register for
PLR - Public Lending Right
This organisation collects royalties from libraries on print publications that
are loaned out to users. Register here.
You may not realise it, but UK tax law requires that all writing revenue,
even that obtained by winning competitions, has to be declared for tax. Details
can be found here.