[molmalo]

Here's the trick for me, using a Galaxy S2, with Android 4.1.2 (JB, but it worked with ICS)

It works with Dolphin and the Stock browser.

1-Open the stock browser

2-Go to Settings->Advanced

3-Check Auto-fit pages

Now, using the stock browser or Dolphin, you can zoom in a page and then, if you double-tap the page, the browser will reflow the text to adjust to the new size.

Note that if you double tap again, it will zoom out. So, to reflow, first adjust the zoom, then double-tap.

Sadly, it doesn't work with Chrome.