SweetFX is a program that helps refining how your game looks, you can control effects like blur, AA, SMAA, FXAASMAA (anti aliasing), sharpening, vibrance, tonemap, curves, HDR, bloom – and more!
It seems that the frames per second drops is minimal.
MoonShades is a game like Eye of the Beholder in the browser.. an rpg, retro style. Currently in Alpha version.
From the same author of Robbie Swifthand And The Orb Of Mysteries!. Darkverse is a space Action RPG.
Naev is a 2D space trading and combat game, in a similar vein to Escape Velocity. Naev is played from a top-down perspective, featuring fast-paced combat, many ships, a large variety of equipment and a large galaxy to explore. The game is highly open-ended, letting you proceed at your own pace.
This is a free game, originally developed by HotPengu(A flash version of the game is there) and brought to the Dreamcast by Senile Team. In this game you control artist Polyko, who has been magically transported into the world of his own creations.
Syntensity, also known as the Syntensity Engine, and previously also called the Intensity Engine, is an open source project that consists of a client, server, and master (metadata) server – everything you need to run your own games or your own virtual world.
Play Dune 2 directly in the browser, as far as i remember this game was the first in its genre. This is a port of Open Dune, an open source implementation of the classic real-time strategy game Dune II.