Answer: everybody!
Up to the beginning of the 20th century, China was very reclusive. It deemed itself self-sufficient, not needing anything from anyone else. China in the 21st century seems to have turned itself 180 degrees and is seeking to network and collaborate with everyone. The list of over 100 countries below has been compiled from on-line articles in China Daily and Xinhua News. They are countries that either sent senior leaders to China or to which China sent senior leaders (often the Prime Minister) in 2012 to discuss and agree collaboration, or with whom China forged or renewed some significant treaty or alliance.
In other words, China is not leaving matters to chance but taking proactive action. Maybe the Chinese leaders have read and internalised Dale Carnegie’s How to Win Friends and Influence People (http://en.wikipedia.org/wiki/How_to_Win_Friends_and_Influence_People) or even Stephen Covey’s 7 Habits of Highly Effective People (http://en.wikipedia.org/wiki/The_Seven_Habits_of_Highly_Effective_People).
On the other hand, maybe China has heard of the saying: “Keep your friends close, but keep your enemies closer.” and since everyone can at some time be a friend or a foe, China wants to keep close with everyone.
By the way, if your country is not one of those listed, either I missed an article OR you better start worrying. 
- December: Mexico, Bolivia, India; New Zealand; USA; Cuba; Kazakhstan; Russia, Iran, Azerbaijan, Latvia; South Africa; Bahrain; Armenia
- November: Nepal, Laos, Pakistan, Maldives, Bangladesh; Cambodia; Luxembourg; Russia; Palestine; Spain; Tajikistan; Benin; Surinam; Italy; Kazakhstan; Kyrgyzstan; Germany
- October: Colombia; The Netherlands; New Zealand; Maldives; Cambodia; Bangladesh; Philippine; Vietnam; Laos; Poland; Romania; Croatia; Moldavia
- September: Vietnam, Russia, Singapore; Myanmar; Malaysia; Turkmenistan; Canada; Cambodia, Sudan, Algeria; France
- August: Bulgaria; Ghana; Taiwan; Indonesia; Brunei; Malaysia; Croatia; Philippines; Egypt; Germany; South Korea; New Zealand; Congo; India; Iran, Myanmar, Sri Lanka, Fiji; Montenegro; Cambodia; Burundi
- July: Cuba; Slovenia; Israel; South Korea; Malaysia; Niger; South Africa; Egypt; Ivory Coast; Equatorial Guinea; Niger; Nepal
- June: Belarus; Georgia: Afghanistan; Myanmar; Laos, Cambodia, Malaysia, Russia; Denmark; Sri Lanka; Belgium; Ethiopia; South Korea; Singapore; Brazil; Congo; Uruguay; Argentina; Mozambique, South Africa, Zimbabwe; Argentina; Poland; Chile;
- May: Kyrgyzstan, Tajikistan, Kazakhstan, Turkmenistan and Uzbekistan; Taiwan; USA, Arab League, Colombia; Japan, South Korea, Romania, New Zealand, Australia; Croatia; Netherlands; Luxembourg; Brazil; East Timor; Singapore; Kenya; Turkey.
- April: Kazakhstan, Britain, Cyprus, Brunei, Premier Wen visit: Iceland, Sweden, Germany, Poland; Thailand, Japan, North Korea, Timor-L’este, Colombia, South Sudan, Indonesia, VP Li Keqiang, presumed Premier-to-be, visited: Russia, Hungary, Belgium, EU, Central & East Euro states, Malawi, Malaysia, Zambia, South Korea.
- March: Britain, France, Italy, UAE, Albania, Angola, Kenya, Israel, Egypt, Brazil, Venezuela, Turkey, Indonesia, South Korea, South Africa, Japan, Cambodia, Taiwan, Ireland, Russia and India.
- February: VP Xi Jinping, presumed President-to-be, visited US; Canada, Australia, Turkey; Taiwan; Myanmar.
- January: Ivory Coast, Pakistan, Germany, Libya, Sudan, Nepal, Saudi Arabia, Kazakhstan; Vietnam; Chile.
CHINDIA ALERT: You'll be living in their world, very soon 