GeForce 9 series

The GeForce 9 series is the ninth generation of Nvidia's GeForce series of graphics processing units, the first of which was released on February 21, 2008. Products are based on a slightly repolished Tesla microarchitecture, adding PCIe 2.0 support, improved color and z-compression, and built on a 65 nm process, later using 55 nm process to reduce power consumption and die size (GeForce 8 G8x GPUs only supported PCIe 1.1 and were built on 90 nm process or 80 nm process).
GeForce 9300 Series.
Geforce 9300 GS.
On May 1, 2008, the GeForce 9300 GS was officially launched.
GeForce 9400 Series.
GeForce 9400 GT.
On August 27, 2008, the GeForce 9400 GT was officially launched.
GeForce 9500 Series.
GeForce 9500 GT.
On July 29, 2008, the GeForce 9500 GT was officially launched.
GeForce 9500 GS.
The 9500 GS is an OEM card that is based on the 9500 GT but geared towards the mainstream audience.
GeForce 9600 series.
GeForce 9600 GT.
On February 21, 2008, the GeForce 9600 GT was officially launched. It was an upgrade of 8600 GTS.
GeForce 9600 GS.
The GeForce 9600GS is a Hewlett Packard OEM card. It is based on a G94a core clocked at 500 MHz. It features 768 MB of DDR2 memory on a 192-bit bus.
GeForce 9600 GSO.
The GeForce 9600 GSO was essentially a renamed 8800 GS. This tactic has been seen before in products such as the GeForce 7900 GTO to clear unsold stock when it is made obsolete by the next generation. Just like the 8800 GS, the 9600 GSO features 96 stream processors, a 550 MHz core clock with shaders clocked at 1,375 MHz, and either 384 or 768 MB of memory clocked at 800 MHz on a 192-bit memory bus. Some manufacturers have mistakenly listed some of their 768 MB models that have 96 stream processors as being based on the G94 chip, rather than the G92.
GeForce 9600 GSO 512.
After clearing the old 8800 GS stock, Nvidia revised the specification with a new core, and 512 MB of memory clocked at 900 MHz on a 256-bit bus. For these cards, the number of stream processors is halved to 48, with the core frequency increased to 650 MHz and the shader frequency increased to 1625 MHz. Some of these cards have 1024 megabytes of memory while still being a 512 model. The revised version is considered inferior in performance to the old version.
GeForce 9600 GTX.
XFX released a 9600 GTX based on the G92 chip featuring 96 stream processors, a 580 MHz core clock, 1450 MHz shaders and 512 MB of GDDR3 running at 1400 MHz on a 256-bit bus. Other than clock speeds, it is functionally the desktop equivalent version of the 9800M GT.
GeForce 9800 Series.
The GeForce 9800 series contains the GX2 (dual GPU), GTX, GTX+ and GT variants.
GeForce 9800 GX2.
On March 18, 2008, the GeForce 9800 GX2 was officially launched.
The GeForce 9800 GX2 has the following specifications: 
GeForce 9800 GTX.
On April 1, 2008, the GeForce 9800 GTX was officially launched.
Taken from an eVGA specification sheet:
In July 2008 Nvidia released a refresh of the 9800 GTX: the 9800 GTX+ (55 nm manufacturing process). It has faster core (738 MHz) and shader (1836 MHz) clocks. Since March 2009 this design is manufactured as GeForce GTS 250.
GeForce 9800 GT.
The 9800GT is identical to an 8800GT, although some were manufactured using a 55 nm technology instead of the 65 nm technology debuted on the 8800GT. The newer (55 nm) version supports HybridPower while the 65 nm version does not.
ASUSTeK have released a 9800GT with Tri-SLI support.
Taken from the Nvidia product detail page.
GeForce 9M Series.
All graphical processing units in the GeForce 9M series feature:
Discontinued support.
NVIDIA has ceased driver support for GeForce 9 series on April 1, 2016.