Beijing
Beijing hates tall skyscrapers, for some reason people think that a rather flat skyline must be 'preserved' in order to mantain the historic aspect of the city. You don't see a relationship between both things? I don't either, but it seems that Beijing is trapped in that mystic height-phobic feeling. We suffer the same issue in most European cities, btw. So don't expect many projects above 250m unless the urban planners mature. I agree with LordChaos80, we'll see their strategy after the Olympics. IMO Beijing should 'accept' a CBD with no height limits somewhere.
Nanjing
I don't know this city very well, seems to be planning a couple of supertalls in addition to Grenland Plaza and like a dozen of 200m+. It's ok.
Tianjin
This one is the new star imo. Tianjin has total support from the central government to become 'the Shenzhen/Pudong of the north'. They are unveiling tons of projects this year, many of them well above 300m. They are building China tallest skyscraper too. Still far below Chongqing in 200m+ towers though.
Shenyang
Shenyang is very close to Tianjin in this race, tons of huge projects coming. However the info is unclear for many of them and seems like they are revising downwards some of the tallest proposals. We'll see.
Wuhan
Long term boom for Wuhan, probably starting in mid 2010s. Wangjiadun CBD seems so promising, but it is just a long term plan.
Dalian
Dalian is probably another coming surprise. By the moment they are building/planning two supertalls and 15~ x 180-260m towers. It is a boom already.
Chengdu
Chengdu hates skyscrapers too (see Beijing). Some 200m~ are coming though and they say they are releasing a 300m~ twin project soon.
Qingdao
Shandong is a huge, rather wealthy province with a very large population. I've always expected Qingdao (or another city) to become a huge city with a lot of skyscrapers. Maybe in a long term, who knows. By the moment Qingdao has just around 10 x 180-240m projects on going.
Jinan
Jinan?? Are you joking?

Jinan isn't even in the top 30 imo.
I can't believe you missed Chongqing. This city has 15-20 x 300-450m and 60-70 x 200-299m projects on going. On the other hand seems like they are taking ages redefining projects once and again, but many towers are being started anyway. World's most booming city only after Dubai imo. I'd vote for this one if you had posted it. There are many characteristics that will boost CQ as a major financial hub in the mid-west. The nearest big city is Chengdu, which is 250km+ away. Chongqing is the closest big city for around 100 million people, probably more. In the coast there are clusters of cities which compete against each other, but CQ is has a unipolar power over the mid-west. So it is likely to absorb almost all the investments and immigrants in the area. Then given the complicated terrain (rocky hills and heavy forests) they are forced to go vertical. I see CQ becoming an innland HK in a few decades.
Wuxi is building skyscrapers like crazy too. Around 6 supertalls planned for a short-mid term and quite many towers above 200m. I don't know how is it possible that a city like Wuxi has such a boom.
Suzhou is another good one. 10 supertalls planned in a long term within its two main CBDs. Suzuhou is one of the 5 largest cities in the Mainland by total GDP as well as GDP per capita, don't underestimate it. Btw, Suzhou is giving a lesson to Beijing since it is also very 'historical' and even so it is planning a crazy skyline.
Hangzhou has also two large CBDs with around 3 supertalls coming.
Changsha is planning around 20 x 200-290m towers, we shouldn't forget about it either.
PS: We can't really forecast which Chinese city will live a huge boom after 5 years. Sometimes one city releases more than 5 supertalls within a few months, as it happened with Chongqing in late 2006, Shenyang in early 2007 and Tianjin in the last 6 months. 3 months ago Suzhou launched its long term plans for its two CBDs and we learned that they are planning 10 supertalls and not just 1.
Who knows, maybe Qingdao or Nanjing will release 8 supertall proposals in the next 6 months. Maybe within 2 years they are deciding that for some strategic issues Xi'an or Urumqi must become a first tier financial and industrial hub and they release a CBD with 8 supertalls. All we can say is that more and more cities are planning and building big skyscrapers.