Yes it applies just as much for digital as it does for film. 99% of motion pictures are shot and projected at 24 frames per second (technically 23.976fps but it's called 24p for simplicity).
If you want proper slow motion then you simply shoot at a higher frame rate and then play it back at the frame rate is it planned to be shown/projected at (as said for cinema this is 24fps). However there are limitations, you need to use numbers which are mathematically compatible. For 24fps projects, 48fps and 60fps are good starting points as they all work nicely (48 / 24 = 2, 60 / 24 = 2.5).
Since most cameras which aren't region locked will normally allow you to shoot at 25p and 50p (for PAL countries) and 30p and 60p (for NTSC countries), 60p is a good option if your project is going to be 24p. However 24p does not suit all types of video, and the majority of TV programs in the UK are shot at 25p. Since 60p does not fit nicely into a 25p time line it's advisable to use 50p if you want slow motion. It's worth remembering though that playing 50p back at 25fps will result in a 50% reduction in speed, whereas playing 60p back at 24fps will result in a 60% reduction in speed.
There is software such as Twixtor which can further help although it is not as good as the method described above as it simply tries to interpolate frames (that is look at two frames, see how they've changed and try to add intermediary frames). You need to shoot in a certain way for it to work well.
As said if you want to go super slow motion you will need a camera which can record even higher frame rates. Some handheld video cameras can go higher than 60fps but normally you have to trade off resolution in order to gain frame rate (the new GoPro HD Hero2 can shoot 120fps but only in SD, and I have a little Samsung HD camcorder which can shoot 300fps but only at extremely low res).
High end digital cinema camera's such as the Arri Alexa can record 120fps at 1080p, the Red Epic-M can record 120fps at 5K (ridiculous!), 300fps at 2K (this is just higher than 1080p). Going even further, a camera which is specially designed for high speed shooting is the Phantom Flex which can record up to 2500fps at 1080p and over 5000fps at 720p.
If you played back 1 second of 2500p footage at 25p, it would last for 100 seconds!
