I suggest using a DSLR for 35mm film scans. Get a good macro lens, a steady tripod, and a light board (or make one) and shot it, one at a time. You get much better results in less time than messing around with a flatbed scanner. Dedicated film scanners are nice, but if you already have a decent DSLR, then that's the way to go. It'll take you a while to figure out a good setup and workflow, but once you've got all of the details figured out, it goes pretty quickly and the results are as good or better as any other method out there.
You can also scan 120 and larger film that way, but once you start to go past 35mm film, other methods start to become more attractive again. You can scan 120 film either as one shot from your DSLR (which sacrifices some resolution, but is still as good as whatever your DSLR is capable of), or you can stitch them together from multiple shots (which can be a bit of a pain sometimes). By the time you hit 4x5 sheet film, scanning with a DSLR is just not worth it. By then, a flatbed scanner made for film becomes the way to go. That will get you good enough results for most things like posting on the internet and prints up to around 20x16. If you need to print something even larger than that, you might consider a drum scan. Though the price and hassle of those machines make them not worth owning, in my opinion. For the rare circumstances where a drum scan is actually necessary, I'd rather just send them out to have them professionally done.
120 film is kind of in that gray area. It's large enough to do on a flatbed scanner, yet you won't get optimal results that way. It's small enough to do with a DSLR, though it can be a real pain to setup. You can buy a dedicated film scanner for it, but those are expensive and don't offer a huge improvement in time and hassle over a DSLR or in quality over a good flatbed. I guess the good news is that any of those methods will work well enough for most circumstances. In any case, the quality of the scan comes more down to your process than to the equipment, so expect it to take several attempts to figure out all of the little tricks involved at getting the most out of your equipment, whichever equipment you use.
