Rishi Smriti

Literally it means "that which is remembered". These are attributed to an author and were passed on from Guru to Disciples over generations. In course of such passages, content do get modified and ascertaining pure originality of any content would be very difficult. Some changes have also been made with malicious intent. 

Based on the nature of knowledge, the smriti literature is of two types: one that expounds sastra and one that outlines codes of conduct, also called Dharm-Shastras. These are next in importance to the Sruti. You can read more about these at (a) sivanandaonline.org site, (b) iskconeducationalservices.org site, (c) hinduamerican.org site. There are 3 well-known Smritis: Manu, Yajnavalkya & Prasara. There are other 15 lesser known smrities.

Different sites mention different names, the table contains more than 18. 

Manu Yajnavalkya Narad
Samvarta Daksha Prasara
Aangiras Likhita Gautama
Atri Vyas  Satatapa
Vishnu  Brhaspati Yama
Aushanasi  Kaatyaayana Harita 
Apastamba Devala  Usana