And for those with disposable income, and who prefer the modeling style of Lego play -- the Lego Death Star just shipped.

If you prefer just free form building, the buckets of bricks are really cheap, compared to the model sets (about US$0.02 per piece, vs. US$0.10 per piece)

As for other sorts of imagination -- I also play various computer games (I love the Zelda series, along with other puzzle games), and watch lots of TV (cartoons and educational programming, mostly).

But as for the OP's question in it, there was the premise--

when you need to work long hours in front of computer

I'd say the most important thing is to not let yourself get to the point where you have a dire need for recharging -- I'm getting old (just hit another one of the 'x0' birthdays today) and I just can't pull all nighters for multiple days in a row like I used to. And I don't want to -- when I realize I'm not making progress, unless I have some major reason for pushing through, I take it as a sign to go rest. Often, my best ideas for a project come from when I'm not directly thinking about it.

Work on your time management, and you won't 'need' to work long hours in front of the computer. (sometimes you will get in the zone, and 'want' to work long hours, but that's a different thing entirely).

Update: As for 'breading' -- yeast breads take too much time and effort (even with a mixer that can do the kneading). I stick with banana bread -- when they start to go off, freeze them, and when you're ready to bake, you can defrost them in the microwave or the sink.