Hello! Sorry, no time to stop by and chat. Gotta keep running...
Blazkowicz's Run (or Run, Blazkowicz, Run!) by Cay Boy - five maps for the Second Encounter. The storyline is simple enough (but at least there is one): Blazkowicz escapes from his prison cell down below and has to make his way to the surface, killing anyone in his way... including Hitler (what is he doing there?) The maps are nice, mostly medium-sized, with decent combat and some non-linearity, enough meat to keep things interesting. The author says the maps were tested under "regorous conditions", though if you want to try for pistol start, you're going to have a rather rough time, especially in the final floor.
RUN!!! is a two-floor mapset for the First Encounter by an unknown mapper. While the first floor simply throws a swarm of enemies at you in four huge rooms, the second level is noticeably better and offers a multitude of fairly interesting combat scenarios. On the flip side, it's rather monotonous in terms of wall textures... But that doesn't make it any less worth trying.
And lastly, Run Wolf, Run! by Cay Boy appears to be simply an earlier version of the first map of Blazkowicz's Run. Cay Boy advertises it as an unique experience, different every time you play it, and it's true that the non-linear layout, coupled with enemies going after you, provide a lot of variety.