I recently did a fresh install of 10.8. Prior to this install, I could rapidly tap twice on my touchpad and, on the second tap, drag the pointer to highlight text. Now, with this new install, that feature is missing. I tried looking in the trackpad settings but couldn't find anything to re-enable this feature.
I was annoyed myself, and found out the answer in the end:
- System Preferences > Universal Access > Mouse and Trackpad > Trackpad Options
- Click the check box that says "Dragging" and you should be all set.
For more details see this CNET article.
By the way, the exact method to perform this action has changed slightly with Mountain Lion.
I have searched all locations which come to mind for enabling such a setting, but without success:
- System Preferences → Trackpad
- System Preferences → Accessibility → Keyboard
- System Preferences → Keyboard
Therefore, I suggest the following alternative:
System Preferences→Trackpad→Point & Click→Three Finger Drag
This way you can highlight text without delay by using three finger touch. If you need to highlight lots of text, you can release one of the three fingers and continue to move the cursor down with that finger.