Most national newspapers have an alphabetical style guide on their website so they are easy to search for specific words. These are useful for checking correct use and spelling of more unusual words.
Style guides can also be entertaining... Check out the list of 'banned' words in The Daily Telegraph for example. The Telegraph's lists 'sensational' or 'distasteful' words that staff and freelance writers can't use as they simply don’t fit the style of the paper.
The Guardian and BBC (pdf download) style guides are useful too for spelling, definitions and journalistic style. The words section on the BBC guide provides good advice for writing as well as broadcasting. It explains some commonly misunderstood words and definitions.
Happy wordsmithing!
