DMOZ is very slow at listing a site. A couple of tips:
1. Make sure you submit once only. Submitting more than once will get you penalized.
2. Make sure your site content fully ready before you submit because you only get one shot in most cases (see #2 above).
3. Make sure you submit to the right and single category. In some categories, you can find the name of the editor in-charge and you can email that editor to see if he/she can speed up the review for it. Signing yourself up as an editor will give you access to email other editors.
To Justin's question, if you're listed in a reputed directory like Yahoo.com, Thumbshots.net or About.com, you may be able to affect the editor's decision (#3 above).