There are 4 office tower projects planned for downtown Houston right now will all 4 set to open in 2010 if things go as planned.
Main Place will be the name of Hines' latest development. Located at 811 Main Street, the building will contain 1 million square feet of space in 46 floors. It will be LEED certified-silver and stand 630 feet tall. Here's the first rendering I could find;
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other projects include the following;
Discovery Tower
30 floors of office space fronting the new 12 acre park with an adjacent garage connected via skybridge. Gensler's design will be LEED Certified as well and contain 871,000 square feet of space on 30 floors. Trammell Crow is the developer and the building will feature ground floor retail. Ground breaking is set for January 2008.
6 Houston Center
Crescent's newest addition to their Houston Center project will rise about 2 blocks from the Discovery Tower on the Eastside of downtown. The tower will contain just shy of 584,000 square feet and rise 29 floors above ground. Ground breaking is set for February 2008. HKS Architects of Dallas is the firm of record.
Additionally, Brookfield Properties is floating plans for 2 other downtown towers. The first would be located at 1500 Smith Street and contain anywhere from 35 to 42 floors. The second and most likely to get built tower is being called the "Gateway Tower" since it will be developed on the far Southwest side of downtown and can never lose its Western views due to Sam Houston Park. The Gateway is proposed to have 30 floors and an rumored tenant has surfaced in Devon Energy.