A NoCD is a type of patch that removes DRM so you don't need the game CD (or DVD) in the drive. Occasionally NoCDs are released from legitimate sources (as with A Vampyre Story and Myst IV) but usually they come from hacking groups that like the challenge of cracking DRM. If you want to find a NoCD for a game, Google the name of the game and the word NoCD. For many NoCD's the instructions are simply to replace the game .exe with the NoCD. Sometimes you have to replace more than one file. NoCD's should be scanned with a virus scanner before using. I've never come across a NoCD that had a virus or other malware in it, but there is always that possibility with anything you download for free.
The intrusive forms of DRM that Microsoft blocks started being put on games around 2003 with StarForce v3. Older games than that won't have the DRM blocked, but the game still not play for other reasons, like not being compatible with a newer version of Windows, or with the drivers that are made for newer versions of Windows. In some cases the disc check mechanism isn't particularly harmful, but just doesn't work on newer versions of Windows.
I will make a list and see if any one wants them and just hope that some of them eventually comes to Steam or GOG.
The Broken Sword games are already at GOG, and have been there for some time.
GOG doesn't seem to like first person games though, so you're not likely to see Schizm or The Omega Stone there.
Scratches used to be there, but was removed. If you already bought it there, it should be in your GOG game list. If not, you may have lost your chance.
GOG's version of Myst Masterpiece doesn't work on any Windows 7 or 8 computer I've tried it on, though their version of Riven does work. Myst III and IV were never available at GOG and probably never will be. If you have the disc version of Myst III, try it with ResidualVM.
CSI games, same issue as Myst III and IV -- Ubisoft owns the rights and isn't interested in re-releasing the games.
The Watchmaker probably won't ever make it to GOG. It was unstable even on the version of Windows it was made for, and I doubt GOG wants to receive a bunch of complaints about it crashing.
The Harry Potter games from EA will probably never be DRM-free downloads because they are owned by EA.
If you enjoyed games like the Kheops games -- Nostradamus, Secrets of Da Vinci, Egypt III, Salammbo, etc... you may find them at other DRM-free sites like fireflower.com and dotemu.com but not at GOG.