
From Mark Wade's Encyclopaedia Astronautica:
Mercury Mark I,
http://www.astronautix.com/craft/mermarki.htm
Gemini, the project:
http://www.astronautix.com/craft/gemini.htm
Gemini, the spacecraft (and proposed variants):
http://www.astronautix.com/craftfam/gemini.htm
Just thinking about this whole repurposing-JV-for-manned-ops issue here, and it got me thinking of the whole repurposing-Mercury-for-two-man-ops idea from back in the day...once ESA's engineers are done retrofitting the interior for life support, seats for the crew, RCS/engine throttling controls, instrument panels, viewports/rendezvous windows -- not to mention the all-important parachute deployment apparatus and heat shielding -- wouldn't they have better spent the cash designing a CTV new, from zero? True, they've proven the basic JV autonomous robotic design, and manuvering systems, and pressure vessel, but still...building that design out for manned flight is certainly a bigger PIA than going the opposite direction, as the Russians did with Soyuz > Progress.
This is pretty much the conclusion NASA came to after all the Project Mercury followup "Mark i/II" proposals to repurpose Mercury for two-man crews, orbital-change manuverability, etc.; if we're going to go this far, why not just design a whole new spacecraft from the ground up? About the only similarity Gemini ended up having was in the command module -- black iconel corrugated hull, cone-joined-to-cylinder shape -- and some of the environmental controls, iirc.
PS @ stizzleswick: I think ESA would do better to try and sell it -- or, more accurately, rides aboard it -- to countries who have astronauts in training but no craft of their own. I'm afraid NASA would still rather be Earthbound than stoop to using something Not Invented Here.