Shapeways and Sculpteo are probably the two most popular print services out there, and both make it really easy to get high-quality 3D prints in a range of materials that ​include plastics, ceramics, and even metal. Different sites are better for different disciplines. Several that come recommended are:

Eat3D and 3DMotive (very reasonably priced) for artists interested in game development, and 3DS Max users. Gnomon and FXPHD for visual effects and modeling, although Gnomon pretty much covers the whole CG spectrum. The price tag on both of these is pretty high, but Gnomon definitely has a year’s worth of good material, and FXPHD actually uses a workshop setting that includes some mentoring. ZBrush Workshops for—yep, you guessed it—digital sculpting in ZBrush. 

There are only two tools more important to a 3D artist than a tablet — their computer and their software package. Although it’s technically possible to paint decent textures and sculpt in ZBrush without a tablet, you’d have to be crazy to want to do it. Wacom tablets start around $100 and run into the thousands, but even their lowest end hardware is rock solid. The Intuos series is a favorite among aspiring pros, but a cheaper Bamboo will certainly get the job done. Of course, artists are always trying to improve, so if you’re looking to buy something a bit more instructional, check out books for 3D modelers and some of the best computer animation books. CreativeBloq and 3DWorld are the best of the bunch, and both contain a nice mix of tutorials, interviews, production features, and artist spotlights that you can’t really find anywhere else. If you’d rather keep things digital, 3D Creative is a fantastic e-zine distributed by 3DTotal Publishing, who have been consistently releasing top-quality material for years. High-quality maquettes from a source like Anatomy Tools are pricey, but they can definitely be worth the investment if the artist is doing a lot of detailed character work. Somewhat cheaper, but no less valuable, is the planes of the head mannequin, which can really help demystify facial anatomy for beginners. As a digital artist, it can be very refreshing to dabble in traditional media from time to time, and of the widely available clays, Sculpey is the most suitable for maquette building and concept sculpting because it takes months to dry and holds details incredibly well. Traditional sculpture can be a wonderful teaching tool for 3D artists who are trying to learn anatomy because it forces a more calculated and analytical approach than ZBrush, where incremental saves and the undo function provide a safety net. Sculpey is available at any craft store — a lot of sculptors find a 2:1 ratio between Super Sculpey to Sculpey Premo produces an ideal firmness and color. This would be very difficult to pull off as a surprise gift, but if you’re not into surprises, ask your 3D-making buddy/relative if the RAM is maxed out on their workstation. If they’re a pro, they’re probably already running high-end specs (by necessity), but budget wary students and amateurs can almost always use a few more gigabytes of memory. Depending on the situation, a RAM upgrade can range pretty drastically in price from $50 well into the hundreds, so you should definitely consult the artist if you’re thinking about going this route. But having said that, there are a lot of smaller (cheaper) pieces of software and plug-ins that can be very useful to a 3D artist, such as Quixel nDo2 and Mara3D Anatomy Reference.