I previously talked about using long exposure for night photography, however you can also use it for daytime photography to get certain effects. Generally you can't do long exposures during the day because there's so much light that there's no way to get your shutter speed slow without greatly overexposing your image. So what can be helpful is a neutral density or ND filter. Basically this is a filter that will block out light which then makes it easier for your to drag out your shutter speed.
Long exposure during the day is often used for flowing water such as waterfalls. This is because the slow shutter speed smooths out the water and gives it a really smooth and dreamy look. So next time you see this effect on a photo of a waterfall you can see how it's done.
Here are some example shots for you to enjoy:
14mm 1.6s F8 ISO 100 ND Used - Sylvia Falls, Blue Mountains, Australia
24mm 8s F7.1 ISO 100 ND Used - Arthur's Pass, New Zealand
76mm 3.2s F9 ISO 100 ND Used - Franz Josef, New Zealand
Long exposure during the day is also a helpful technique for people shooting in public places where you don't want people to be identifiable. You can make your shutter speed longer by making your aperture small. However, be careful not to make your aperture too small because you can make your image lose sharpness because really small apertures cause light refraction which can soften your images. If you don't have an ND filter, you can also use the multi-exposure mode on your camera if it has one and use the average blending mode and then take a bunch of shots. Then your camera will effectively average your exposures which will give the same effect as if you had a really long shutter speed.
18mm 0.6s F22 ISO 100 - Sergels Torg, Stockholm, Sweden
18mm 1/2s F22 ISO 100 - Kungsgatan, Stockholm, Sweden
So hopefully that's something else for you to try out when you get the chance.