LG is the main producer of IPS panels. Samsung makes PVA panels for the high end stuff (highest static contrast of any LCD type, up to 1:2500!). Both panels are suitable for wide viewing angles and vertical mounting.
TN is the stuff you see in the computer store on the corner. Most people buy this. Cheap, fast, but less accurate with colours (the technology is only 18-bit colour, all the rest is done with dithering or PWM), and horrible viewing from either below or above, thus horrible mount vertically.
LG IPS panels are used by NEC, EIZOs, DELL, ViewSonic, Philips, Apple, HP, older LG's, older Acers to name a few
Samsung PVA panels can be found in older NECs, EIZOs, older DELL's, a few Samsungs, older Acers, iPads, LaCie.
As you can see, many brands dropped the high quality screens. Samsung only sells the F2380M C-PVA now I guess, LG does not sell their own high quality screens under their own name any more. They both had great displays two years ago. Samsung 213T, 245T, 275T, LG W2600HP, LG W3000H to name a few. All discontinued in favour of making pennies on TN bulk.