As promised, mobile WiMAX is now available in Chicago through Sprint and Clearwire.

Clearwire started selling the service yesterday, according to reports from the Chicago Tribune, with Sprint announcing today that mobile WiMAX also would be available under its own brand. Comcast will begin reselling the service later this fall.

In addition to Chicago, Sprint also launched in a smattering of other markets, including Charlotte, N.C.; Dallas-Ft. Worth; Greensboro, N.C., and Raleigh, N.C. The carrier plans to launch mobile WiMAX services in Boston, Houston, New York, San Francisco and Washington, D.C., in 2010.

Sprint also began carrying its first netbook, the Dell Inspiron Mini 10. The 3G netbook is priced at $199 with activation on a Sprint Mobile Broadband plan and a two-year service agreement, after a $100 mail-in rebate.

The netbook is currently only available in the Baltimore area, the first market where Sprint launched 4G service. Sprint did not provide details as to the future availability of the netbooks in other markets.

Sprint is struggling to cap widening losses, a problematic churn rate and customer defection. Last week, the carrier said it lost $478 million in its third quarter on a 9 percent drop in sales. Sprint’s churn rate hit 2.17 percent and it lost 135,000 subscribers.

In addition to its troubled financial state, Sprint recently lost its contract to provide connectivity for Amazon’s Kindle, which will now run on AT&T’s network.