If you don't know about polarizing filters The Luminous Landscape has a good section about polarizing filters. If you do much landscape photography a polarizing filter is very helpful.
In the post on Tuesday I forgot to mention that most of the time I use the fish-eye attachment with the Holga HL-C when using a camera that is not full-frame. With the smaller sensor there is no fish-eye effect, however there is an amount of distortion that I like.
That's all for today.