http://www.detailedimage.com/Poorboys-World-M1/Natural-Look-P34/16-oz-S1/
or
http://www.detailedimage.com/SONAX-M49/Dashboard-Cleaner-P541/250-ml-S1/
are my go-to products. Although there are obviously tons of others.
I like the Poorboys for older or more rubbery parts that need some moisture injection, and the Sonax for newer, harder, "high-tech" plastics.
PM me for a 15% off code for the detailed image site.