Reddit mentions of B+W 77mm ND 3.0-1,000X with Single Coating (110)

Get a 77mm variable ND filter (it changes strength as you rotate, much like a circular polarizer) and get yourself a series of Step Up Rings to convert from 52mm (which I assume your 30/1.4 is) to 77mm.

The biggest lenses you'll likely ever own are a 70-200mm and a 24-70mm, both of which are 77mm filter threads (at least the Nikkors are), so if you buy filters in that size, you can just get step up rings to adapt your filters to your smaller lenses.

I recommend spending money on nice B+W filters. If taken care of, they'll never ever be obsolete, so you might as well get quality: http://www.amazon.com/77mm-3-0-1-000X-Single-Coating/dp/B003ZDHP7U/ref=sr_1_1?ie=UTF8&qid=1347401507&sr=8-1&keywords=B%2BW+77mm+ND

Then buy a set of cheap step up rings that fit your various lenses.

A good 150mm rectangular filter is going to blow about your entire budget.

One can make a filter holder by cutting out a sponge and spray painting it black with the remaining $5.

I haven't the faintest idea why every filter holder is $150-$300. It's some machine shopped aluminum, should be $30.

Correct me if I'm wrong, but the 17-40 is a 77mm screw front. That's a very common size and therefore a decent investment, should be easy to find a circular filter for ~$50-80. I'd recommend B+W 10 stop for $60.

10 stop ND filter

They are ridiculously fun to play around with.

If you're looking for a screw-in filter, B+W is the way to go. Just make sure you get the size that fits your lens. Never really had any color casting issues with it, even on their ND 3.0 filter. Personally, I find myself using a ND 1.8 more often though I have both. There are also drop-in filters like those made by Lee, which come highly regarded but are leaps and bounds more expensive. Multi-coating is nice to have, but more important for polarizers than filters. It really depends on how much you're willing to spend. I have no idea what a "hot mirror" is, but I'm thinking that you're referring to a hot sensor or hot pixels. When you take long exposures, with an ND filter for example, the sensor will continue to heat up as long as the shutter is open. Hot sensors produce more noise, which hurts overall image quality. Any filter you put in front your lens is going to have some adverse affects on your image, most of which can be easily fixed in post processing. Contrast, tones, and all that can be adjusted in Lightroom after the fact.

I just keep a CP, a 10 stop ND, and a square 3 stop Grad ND in my bag, all in the size of my largest filter (77mm), with adapter rings to adapt them down to my my other lenses. Haven’t found much need for anything else.

I once carried the full set of solid 1,2 and 3 stop NDs with their graduated counterparts, but found I never used them given the ability to really do good highlight and shadow recovery in Lightroom. and the adjustable ND was terribly gimmicky and cheap. Just settled on the B+W 1000x ND filter and have been very pleased. Minimal cast, but very correctable in post.

I ended up getting a B+W 77mm ND 3.0-1,000X. I've been very happy with it.
http://www.amazon.com/gp/product/B003ZDHP7U/ref=pe_62860_33420350_email_1p_1_ti

I used the b+w 10 stop ND http://www.amazon.co.uk/77mm-Neutral-Density-Filter-Stops/dp/B003ZDHP7U/ref=sr_1_2?ie=UTF8&qid=1376313787&sr=8-2&keywords=10+stop+nd+filter

I want to buy an ND filter for daytime long exposures, but can't decide on what to get.

At first, variable ND filters made sense - because they would enable me to shoot wide open in daily shots, besides long exposures. I'm a hobbyist, so the little degradation in quality with vari-NDs wouldn't have mattered, but the x pattern issue really discouraged me from wanting one.

Anyway, I can't decide between these three ND filters:
Hoya
B+W
Another, more expensive B+W - what's the difference between this and the previous one?

And here were the vari-NDs I was considering:
Tiffen
*Light Craft Workshop

As I said, I don't think the vari-NDs are for me.. but which of the other 3 would you recommend? Any loss in sharpness and contrast? Any color casting?

I would not prefer to go up to the pricey B+W's range of $150, but if there's a big difference in image quality compared to the other two, I just may choose that one.

I'm a bit in your same situation. I'm going to Iceland for 12 days and going to try and shoot a ton of landscapes with my Canon 60D and Tokina 11-16mm Ultra Wide angle (uses 77mm filters). Here's what I got on a budget from a little digging on Amazon.com:

Tiffen 77mm Circular Polarizer: $144; on sale for $20!

B+W 10 Stop Neutral Density filter: $252; on sale for $100

Tiffen 77mm Neutral Density 0.9 Filter: $99; on sale for $25

Step-up and Step-down rings let you use your pricey filters on your other lenses; saving you lots of $$$!
Fotodiox 7 Metal Step Up Ring Set, Anodized Black Metal 49-52mm, 52-55mm, 55-58mm, 58-62mm, 62-67mm, 67-72mm, 72-77mm: $13.49

Fotodiox 7 Metal Step-Down Ring Set, Anodized Black Metal. 77-72mm, 72-67mm, 67-62mm, 62-58mm, 58-55mm, 55-52mm, 52-49mm: $14.60

Pedco UltraPod II Lightweight Camera Tripod: $16.67 instead of a $100+ Gorillapod

You can go super cheap/artsy and use welding glass as a ND filter: $6 There's lots of easy tutorials on how to fix the color tint of the glass online.

Travel and photography are both amazing yet expensive hobbies. I hope my little list helps you out by saving you a little $ on the photo side; letting you have more $ on the travel side to do and see more... thus getting more amazing shots!