Microgaming has been around since 1994 and was, as a result, the first online software provider targetting the online casino space (the first ever online casino was also powered by Microgaming). You will find their games in more than 500 casinos today with some being exclusively powered by them (like Roxy Palace Casino) and most of them using just their slots (via their QuickFire platform).
With over 500 slot games developed, some of them can be played via their download product only (found at Roxy Palace Casino and 32Red Casino for example). However, all their popular titles can be played in your browser and most casinos which is good including favourites like Immortal Romance, Thunderstruck II and Tomb Raider Secret of the Sword. You will also find that a lot of their classic slots (like Loaded) are being revised and made into high definition.
Microgaming has definitely stepped up their game recently with newer slots showcasing new bonus features and much better graphics/animations. They have branded titles like Jurassic Park, Game of Thrones and Terminator 2 which are brilliant.