Whenever I have time, I always check out ExpiredDomains.net to see if there are any domain names that I like. These are usually some great finds for your niche as they have already been indexed and established. This makes them easier to rank with the search engines.

Try and find domains that have backlinks from .edu, .gov, or from major websites like CNN, Time, or ASK. You can use the site to quickly sort websites that have a high page rank, lots of back links, as well as a high Alexa rank.

Usually I like the expired domains to have at least:
» TF: >15
» CF: 15 or <30
» PA: >20
» DA: >20
» Age: 2 or more years old
» Clean anchor history (No Spammed Backlinks)
» Not previously used as PBN (Public Blog Network)
» No korean, asian or japanese
» Quality and clean links

Play around and see what you can find. It may get you some easy traffic to your new niche site.