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Check out the Chandra Emission Line Project web page: http://cxc.harvard.edu/elp/ELP.html

A few of the many recent observations with Chandra that show the richness of the spectra, and the need for more precise calculations are given below. In general, Chandra is demonstrating the need for better theoretical X-ray spectra for a wide variety of objects, including comets & planets (fluorescence and charge-exchange) to stellar coronas, supernova remnants (non-equilibrium effects are especially important here), accretion disks around stellar and supermassive black holes, and galaxy clusters.

http://xxx.lanl.gov/abs/astro-ph/0202083
Resolving the Composite Fe K-alpha Emission Line in the Galactic Black Hole Cygnus X-1 with Chandra, J. Miller et al.

http://xxx.lanl.gov/abs/astro-ph/0201533
The Chandra LETG and XMM-Newton Spectra of HR 1099 M. Audard et al.

http://xxx.lanl.gov/abs/astro-ph/0111132
High resolution Chandra HETG and RXTE observations of GRS 1915+105 A hot disk atmosphere & cold gas enriched in Iron and Silicon., J. Lee et al.

Astrophysics, abstract
http://xxx.lanl.gov/abs/astro-ph/0110634
The Chandra High Energy Transmission Grating Spectrometer probes the dusty warm absorber in the Seyfert 1 galaxy MCG--6-30-15, J. Lee et al.

http://xxx.lanl.gov/abs/astro-ph/0112037
Chandra X-ray Spectroscopy of Kes75, its Young Pulsar, and its Synchrotron Nebula
Authors: B. F. Collins, E. V. Gotthelf, D. J. Helfand

http://xxx.lanl.gov/abs/astro-ph/0106002
Title: Direct Detection of Warm Dark Matter in the X-ray
Authors: K. Abazajian, et al.