Yesterday, I installed a new (and currently free) app from Autodesk onto my iPhone, called Autodesk ForceEffect(check it out in the App Store).
With this app, you can draw a 2D schematic of beams, nodes and forces. It will allow you to quickly assess the reacting forces into a structure. The examples included with the app also show you that a photograph can be used as an underlay, to sketch on top of them, e.g. to check a structure in the field.
While the iPhone screen is quite small for my not-too-small fingers, it works quite handy: there are automatic guidelines that constrain the direction and alignment of nodes you draw. You can switch units between metric and imperial and use gestures for scaling (pinch), panning (two finger swipe) and editing (single touch). Moreover, while it is hard to sketch an exact size for a truss, you can fix the length be entering the exact value on the dimension line and this will be enforces, even when you start moving nodes around.
Click on a truss, and you get the acting forces (in color, with direction to show pressure or tension).
You can generate a report, which could be used to help you enter the exact nodes and sizes and forces in a FEA software afterwards, when you want to go a step further.
This is exactly the type of app I would have loved while being an architectural engineering student, quite some years ago. It’s intuitive, interactive and free (for the moment?). You’ll need an iPhone, iPad or iPod Touch to be able to use the software, but I wouldn’t be surprised if they will port it to other devices in the near future as well.