Over on his blog, Nobu has uploaded a post showing his experiments with a forced air cooled RTL-SDR dongle (note the blog is in Japanese so use Google Translate). A tiny fan from RS components is attached to the case of the dongle and draws power from the dongles own power regulator. Nobu also replaced the crystal oscillator with a flat packaged oscillator for a better fit.
The translation is a little difficult, but it appears the fan was able to successfully stabilize the temperature. This may be an alternative to the temperature controlled oscillator (TCXO) RTL-SDR modification.
EDIT: It seems that the fan is not to improve temperature stability, but rather to improve sensitivity. Nobu has referenced this experiment which shows that improved heat dissipation improves the dongles sensitivity.