Red Alert

As well as the link from this post's image it may also be helpful to see this page about how to play Red Alert without burning it onto a CD. Red Alert is a great old game, that was released as freeware to mark the release of Red Alert 3. I spent many days playing it when it was first released, and since rediscovering it I have spent many hours more. Compared to some of today's games standards the AI can seem quite stupid, but I think the range of units and buildings in this game still makes it one of my all time favourites.

Zombie City Tactics

Zombie City Tactics is a turn based strategy game themed around a zombie infested city. It plays a little bit (but not much) like chess - with the humans and zombies taking it in turn to move their pieces around a grid. There are three types of humans - bog standard one square per turn, soldiers who take a piece without moving, and slayers who can move two spaces per turn. They can be dropped into the playing field, but cost different amounts of energy to summon. The energy is gained by holding land against the zombies and so there's a balance to find between all out offence and simply staying put. Overall the game is nicely put together and the 3D layout is pretty cool.

Wordle

Create a cloud of words using a website or text document as input. Style it how you like and then astound your friends and family with your skills. This could be useful if you want to create a tag cloud, or maybe if you want to find out the important elements in a story without reading it... Or (more likely) it could just be something to play around with for a couple of minutes and then throw away.

ASCIIpOrtal

ASCIIpOrtal is a 2D ASCII version of Valve’s Portal. Run around, fire portals, jump through portals, dodge barrels, push switches and enjoy the company of your companion cubes... all in wonderful text format.

Interestingly (or not really) the character set used isn't ASCII - for instance the green player character (see Wikipedia). Also the game's author lists his inspirations as "Increpare’s Portile game, Super Serif Bros, and Valve’s Portal". So it's not ASCII, nor is it just Portal, but it is definitely awesome.