I've been doing some statistical analysis of the suggested sites that get listed in the ODP, and reached these conclusions:
- Sites that are submitted to the "right category" (meaning the category where they ultimately get listed) get listed four times faster than those submitted to other categories.
- Only 31% of the submissions that get listed are suggested to the "right category".
Important note: the results above apply only to those sites that eventually get listed. It is not necessarily related with the likelyhood of a site getting listed. Also, they are the average for the whole directory; the exact results may vary between categories.
Now, the obvious question is "how do I find the right category?" Sometimes that can be hard, but please do your best to follow the submission guidelines and submit only to the single best category. It is especially important to submit to the most specific category possible for your site, because submissions to categories that are too broad will wait much longer before an editor looks at them and sends them to the right category.
Some hints: look at the sites that are already listed in the category that you are considering, to see if they are similar to yours in topic; conversely, if you know of other sites that are similar to yours in topic, see in which categories they are listed.