Pinterest is valued at $3.8 billion

"According to several sources, Pinterest has completed another enormous funding, this time nabbing $225 million with late-stage investor Fidelity Investments in the lead.
The new infusion of cash — which comes on the heels of a very recent and massive funding in February of $200 million that valued the social scrapbooking company at $2.5 billion — pegs the latest valuation of Pinterest at $3.8 billion."

Source:  AllThingsD, 23rd October 2013

Earlier - $2.5bn in February