ColorHug is the Best Answer
Linux developer Richard Hughes has designed and sells an open source colorimeter called the ColorHug. If you are running Linux, and don't have other hardware available already, this is simple, cheap, and fast. (In fact, it's about 50× faster than the old GretagMacbeth I was using before.)
The current price is £60 plus shipping (each device is hand-assembled in the UK). You may actually be able to get one of the older Xrite/GretagMacbeth devices for a bit less, but unless you're really strapped for cash, the better experience of the ColorHug is probably worth it — and you'll have hardware and software designed to work together, rather than reverse-engineered.
But, you might find one of these devices very cheaply, or have one already. In that case:
If You Have Another Device
Gnome Color Manager (now part of colord) can use Argyll CMS, but it also supports the Pantone/X-Rite Huey natively. According to the Gnome docs, the profiles produced natively aren't great, but it's easy. If you're using newer Gnome (3.x), it's been re-written and appears to have options to give better results with the same ease of use. I have a GretagMacbeth (now bought out by X-Rite) Eye-One Pro device, and it doesn't seem to work at all with even the new version, though — so maybe you still need the Huey.
Anyway, PeterT pointed out a program called dispcalGUI, which is a cross-platform GUI front end for ArgyllCMS. It's still a little intimidating and not nearly as slick as Gnome Color Manager, but it's really easy to use once you spend a few minutes going through the quick setup and usage documentation. Works nicely with the device I have and produced good results with little fuss. See this question for some after-you've-calibrated-and-profiled usage info on Linux.
Oh, and also from the dispcalGUI docs, a list of supported instruments:
- X-Rite ColorMunki
- X-Rite DTP92
- X-Rite DTP94
- X-Rite/GretagMacbeth Huey
- X-Rite/GretagMacbeth i1 Display 1
- X-Rite/GretagMacbeth i1 Display 2/LT
- X-Rite/GretagMacbeth i1 Monitor
- X-Rite/GretagMacbeth i1 Pro
- X-Rite/GretagMacbeth Spectrolino
- Datacolor/ColorVision Spyder 2
- Datacolor/ColorVision Spyder 3
And some notes on a few of these, based on research I've done:
ColorMunki Design/Photo is expensive ($450), and is a spectrophotometer rather than a colorimeter — it reads wider bands of colors at once, and can be used to measure surfaces like paper, not just monitors. I can't find the reference right now, but one review I found was very disappointed in the results. (I'll update this once I find it.) See below for the ColorMunki Create, though, which is a different product.
X-Rite DTP-94 — this is discontinued, but is one of the few to offer glass color filters rather than the dyed ones found in other instruments. Theoretically, this should last longer (the others may lose accuracy over time). And in general, this gets lauded as having the best results. The caveat, though, is huge — it's not as good for LCD screens as for CRT monitors, and wide-gamut displays are right out. Dunno if you can even find this anymore at non-crazy prices.
Pantone Huey — no particular note other than the one above (direct GCM support), and to mention that it can be had for as little as $55 new if you're lucky. (The Pro version is the same hardware with different, irrelevant-to-us software, and that's not too expensive either at about $80 shipped.)
X-Rite/GretagMacbeth i1/ Eye-One — I have the "Pro" model of this. It's an early revision, so it's pretty slow. I'm happy with the results visually even if it is a few years old; so if there is any filter color decay it's pretty subtle. All the i1 models listed (and the ColorMunki Create, and apparently also Lacie Blue Eye) work basically same way under Argyll CMS. The Pro model has a high-resolution mode which should give somewhat more accurate results. And my old model is quite slow — taking about 4 hours to do a high-quality calibration and profile! — but newer models are apparently faster. But wait! – don't confuse this with the similarly-named i1Display Pro (see what they did there? gah!) which is apparently entirely new and not supported yet (it's more expensive, so you're unlikely to get it by accident). X-rite Versions of this are roughly $135 new; the ColorMunki Create looks like a deal at $75 (and it was briefly down to $65; maybe it will be again).
Datacolor Spyder 2 / Spyder 3 — the main note is that the Argyll CMS docs say that the maker of these devices, "appears to be hostile to the use of these instruments under Linux", so I think I'd stay away since there are other options. (And using the Spyder2 at all requires pulling loadable firmware from the original installation software, which is less than convenient, although discalGUI has a straightforward-seeming option to do so.) Users of other operating systems seem to like the Spyder 3 over the X-rite offerings, though, and it is competitively priced at about $65 for the version without an ambient-light sensor (or about three times that price if you do want the ambient sensor + fancier proprietary software).
The Bottom Line
The ColorHug isn't necessarily the absolute cheapest, but works very well and is actively supported. Unless you have easy, cheap access to another device, my recommendation is to just go with that.
For non-Linux solutions, the market situation is confusing, and it's hard to straighten out the hardware. However, it looks like basically all the competing companies who used to make things have collapsed into just X-Rite and Datacolor, and all of their current and recent colorimeter products (that is, the affordable ones!) work. The X-Rite Huey is generally cheaper, but the X-Rite Eye One products, in all the different names, can also be found below $100 as well, and may be a little better. Datacolor's Spyder products are to be avoided if you care about open source, but do also work (with the later versions being less of a hassle).
Disclaimer: I now work for the same company Richard does, although mostly in different areas and none related directly to ColorHug (which is a side project of his).