Lens Filters...

For a general protective filter, I usually just go with the cheapest. I haven't noticed any difference between that $6 Tiffen and the much more expensive one that came with my camera. For other filters, you might have to shop around. Someone gave me some extra magnifying filters they had that were very, very cheap and when I compared them to the ones I use normally (can't remember the brand) and had thoroughly reviewed before purchase, there was a noticeable difference. I'm sure someone else will have a better idea of what brands, in general, are best and which ones are a better money-quality balance. Online reviews are your friend.

The only filters to consider when using a digital camera are the UV filter (for protection), the circular polarizer (to diminish reflections, improve saturation -- notably skies) and neutral density (in cases where there simply is too much light to achieve what you want). All others can be mimicked artificially in Photoshop. There really is no point in buying a 500$ lens (or more, or much more) and putting a cheap filter in front of it. You will be degrading the quality of the image -- usually softening the image. (And if you don't care about sharp images, then don't invest a lot of money in lenses in the first place!) Excellent filters are made by Schneider Optics (better known as "B+W") and Heliopan. They cost more, obviously, but you get what you pay for. All my lenses have a B+W UV filter sitting on them permanently for protection, and I also use a B+W circular polarizer when needed. Some of my lenses share the same filter size, so I can use the polarizer on more than one lens easily.

I've used a variety of brands at a variety of prices. My basic rule of thumb after trying several, is that anything made in Japan is usually good. Anywhere else, you're taking a gamble it seems like.

I am a big fan of Cokin filters. The best part about them is that they're adaptable! If you spend $50 on a filter, you're not just limited to using it for one lens! You just need to get different ring adapters for all of the different lenses you use! That is A LOT cheaper than replacing all your filters every time you get a new lens! If you're looking into a specific filter, but want to see it in action before you buy, a great way to do that is to go to Flickr.com and search the name of the filter you're interested in. Then in your search results, you should see lots of example images taken by different photographers using that filter! You can also do this to search for cameras, lenses, any type of photography equipment! It's a great way to see it in use before you buy!