Any Western Digital Blue or Black series drive. Avoid the green series, as they are slow pieces of junk. Seagate also makes decent large drives, as does Samsung and Hitachi. The more cache the better, the faster the drive will perform regardless of rotational speed. 32MB cache at a minimum. Now that being said, if your motherboard supports it (and it does) you may want to get two of the drives and install them in Raid 1 mode. If you get 2, 2 TB drives, this gives you a final drive size of 2TB, but all your data exists on both drives. If either of the drives fail, you still have all the data on one of the drives, and it will automatically rebuild to two drives when you replace the failed drive.
Solid state drives are all about speed. They halve your boot time. Any game that loads data from your drive will perform quicker. Programs will generally open faster, and large files will save and open faster. You use them as your primary Operating system drive and also install any programs you use frequently on them. I have a Crucial SSD in my main computer, and its much faster than my previous pair of Raid 0 15,000 RPM Sas drives ever was. There are basically three types of SSD's, ignoring alot of subtypes: The Intel created ones, the Corsair "Sandforce" controller style ones, and the OCZ abominations. Never buy the OCZ drives.
That particular samsung one is essentially exactly the same as my Crucial one, but about half the capacity, 120GB is doable for an operating system and games, unless you tend to install more than12 large games on your computer at a time. A SSD is the single most effective noticable hardware speed multiplyer available at the moment in that price range. I tend to hover at a 140GB OS partition personally, with a pair of 2TB rotational drives in Raid 1 for primary backup, which in turn feed to the network attached storage device 2TB array for additional backup. At any point, any file on my computer that has existed longer than 24 hours is located on at least 6 different hard drives.
Things to look for when buying a SSD, SATA III or 6GB per second is good. your motherboard should have a 6GB / second SATA III port on it. you want to make sure the SSD is attached to that port otherwise it will operate at half speed. SLC vs MLC, SLC is better, but insanely expensive. almost all drives you see are MLC. has to do with the number of stacksd of memory chips. you can pretty much ignore it. If you look at the Intel vs the Sandforce style drives, generally the Intel ones are about as fast, they have a few things they are faster at, a few they are slower at in terms of file operations, and they handle TRIM commands a bit differently. (TRIM basically being the garbage collection routine of a SSD. long story short, SSD's work differently than rotational hard drives and need to recover empty space periodically to stay fast, older drives that didn't support TRIM would slowly lose about 30% of their effective speed over time until you reformatted them and started over again.)