Simply because it was one of the cheapest accessories I could purchase, I've just bought a polarizing filter (a Hoya Pro1 55m) to go on my kit lens. So, this week I've been playing with filters. The Hoya definitely adds a depth of colour. So I played with this a bit doing some indoor shots (although this is really not what a polarizing filter is best for - think sky and water, however I liked the grittiness it added to the shots). Then I played with photoshop's built in photo filters...so filtering already filtered photographs...and then I ended up converting to B&W so probably all completely pointless!
Here's the b&w version and the colour one is in my flickr account. Out of the two I'm not sure which I like best. As for the subject matter, may be a bit conceptual, but makes sense to me at the moment!