Like a family tree maker or something like that, with dual line relations. I have no idea if that makes sense to anyone but pretty much like so:

|------------------|              |--------------------||                  |-----hate---->|                    ||                  |              |                    ||George Washington |              |    Cows            ||                  |<----Love-----|                    ||                  |              |                    ||------------------|              |--------------------|

A free one, if you know of one would be great.

Wouldn't any flowchart program work for that? Or a vector graphics program, if you know how to use one?

Personally I'd just draw it on paper with colored pens or markers if it was a diagram for internal use, but if I wanted it to be pretty and official-looking I'd use Inkscape. If I had Visio and knew how to use it that would also be a good choice. I've also heard there's a particularly good flowchart software that's only for Mac. If you don't have or know how to use any of those, an easy-to-learn by feature-limited alternative would be one of the free mind-mapping softwares available online.

I'm going to get Visio from my school, but it doesn't have an option for two lines in between entities, as far as I know. If I can't find anything else, I plan to use Visio.

I used to do it on paper, but I want something that would be easily changeable. So I don't want to hand draw it or on a bitmap in Paint.

Visio doesn't let you add connectors from any corner of one object to any corner of another object, or that sort of thing? If not, then it's not very flexible.

Actually my best friend was just complaining about this sort of thing a week or two ago, he had to make some sort of organizational diagram for work and said that when he researched it he didn't find any free software which made diagrams which were pretty, easy to make, and easy to edit. I use Inkscape but it flunks the easy to make part - not really a problem for me since I already know how to use the software well and the diagrams I make are usually for some sort of tutorial or documentation which doesn't have to be changed much. So I make a rough sketch if I'm not quite sure what I want, then I make the diagram as a piece of vector art. But for someone who didn't know how to use a vector art program I bet it would be frustrating to try to use Inkscape to make flowcharts - it's not set up to do that, so it's not anywhere near as automated as one would hope. Flowchart making functionality is on the developers' "to do" list, but so are a thousand other things.

Not sure if this helps but Dia is a good alternative.

http://projects.gnome.org/dia/

Dia looks like something that fits it, at least that's how the screenshots are pointing to. I can't tell without using it though. Thanks for that.

Edit: This definitely works, it's too bad it's a bit slow. But it is the best I've seen. I might go back and forth with this and Visio.

[Edited by - pothb on December 24, 2010 4:54:27 AM]

Graphviz?

It's a text input system (so you can automate it), various solvers to lay the diagrams out, and the output can be images, pdfs or SVG which you can then edit in Inkscape.

Graphviz looks like it can do what I want but it's not simple enough for me it seems. So I don't think it'll help me in this regards.

Thanks anyway, though.

Visio have the option to draw relationship diagram. Check out the latest version of Visio i.e. Visio 2010. It’s a great diagramming software, which I use it for creating business process diagrams.
http://visiotoolbox.com/2010/mashups.aspx

OmniGraffle is one of the best peices of software along these lines that I have ever used. Unfortunately, it is Mac-only, and not terribly cheap - but definitely worth a look if those two points don't bother you.