Mainly looking through memorial pennies at the moment but anything will help in the long run I use http://coinauctionshelp.com/forum/viewtopic.php?t=1140 and it is very helpful but I feel like I'm missing out on a lot of other errors and varieties. Also, it doesn't seem to have been updated in a while unless 2019 and 2020 were quiet years for the penny. Also, what are your opinions on the shield penny? It could just be me being born 9 years before it was put in use but I miss the memorial penny so much. The shield penny doesn't feel lucky to me.
Here are some good ones to bookmark www.doubleddie.com www.varietyvista.com www.lincolncentresource.com www.error-ref.com www.coppercoins.com www.cuds-on-coins.com I'm sure others will add more Hope this helps
@Oldhoopster pretty much covered it. Also try to do a search online. I use Bing instead of the forced Google search engine and often get different results.