For various reasons, the technique was not developed further by others, and was eventually pushed aside by developments such as Autochrome, Kodachrome, and so forth. But when the Russian Revolution hit, Prokudin-Gorskii escaped the country with much of his work, finally settling in France. His heirs later brought his plates and photographs to the United States, and sold them as a lot to the Library of Congress in 1948. After remaining in storage for some time, the plates and photos became part of a major exhibition by the library in 2001, and have taken a permanent place on the library's website. They offer us a detailed glimpse into an environment that has been lost to time.
The Library of Congress, thankfully, has re-inverted them so that everybody's not standing on their heads (along with converting their scans from negative to positive). That can be confusing while assembling the pictures though, because it has the effect of also reversing the traditional RGB order (they are thus RGB bottom-to-top, but originally top-to-bottom because the camera recorded inverted images).
One of the best characteristics of these images is their copyright status. All taken prior to the Russian Revolution in 1917, they have public domain status from sheer age alone. Added to that, the LOC actually purchased these plates from Prokudin-Gorskii's heirs in 1948 and now distributes them gratis from their website.
On the downside, many of the images have been damaged; this is unsurprising given their extreme age. Many more have been lost altogether (in the three-color state) and are represented in the Library's collection by single grayscale photographs which have survived. We therefore need to do the best we can with what we've got.
Prokudin-Gorskii himself didn't have any technical means to make prints of these photographs, or put them on the web for the world to view; he displayed the colors by using a triple-lens projector and gels, for a small (but no doubt captivated) audience. That's where our advantage comes in: digital manipulation. We can take it as far as we like.
The tutorials were done in Adobe Photoshop version 7 for the Macintosh. If you're using something different, your mileage may vary accordingly.