Here are some links:
Mark Wiens: "Jua Kali – The Informal Kenyan Sector for 'Git Er Done'", July 24, 2011
http://migrationology.com/2011/07/jua-kali-kenyan-informal-labor-sector/
Book:
Kenneth King: Jua Kali Kenya: Change and Development in an Informal Economy, 1970–1995, 1996
http://www.ohioswallow.com/book/Jua+Kali+Kenya
Book:
Steve Daniels: Making Do: Innovation in Kenya's Informal Economy, 2010
http://analoguedigital.com/makingdo/
Reviews of "Making Do" (2010):
Mandy de Waal: "New book on Kenya's informal sector, some great lessons", 22 Sep 2010
http://www.dailymaverick.co.za/article/2010-09-22-new-book-on-kenyas-informal-sector-some-great-lessons/#.U0z75cdkj-k
Jenara Nerenberg: "Africa's Informal Economy Revealed: New book synthesizes activities of informal product designers", August 23, 2010
http://www.fastcompany.com/1684394/africas-informal-economy-revealed
Steve Daniels: "African Tech Makers: Selections from the New Book Making Do", Aug 27, 2010
http://www.theatlantic.com/technology/archive/2010/08/african-tech-makers-selections-from-the-new-book-em-making-do-em/62143/