The industry standard for CD Images is the ISO, but they are usually ripped by people who use programs with their own proprietary formats. The table below gives the name and website of each native format, most of these programs will allow you to burn the images or convert them to ISO. Many of these programs require paid registration, we must remind you that using a site such as Free Serials to obtain the serial number or a crack for these programs is software piracy and we do not condone that sort of thing ;)

Extension	Program	Company	Website	Notes
RAR / ZIP / 7Z	7-Zip	7-Zip	http://www.7-zip.com	These are NOT CD images, but contain the images INSIDE these files. You need to decompress the file with 7 Zip to get to the image.
ISO, BIN+CUE, CCD, MDF, NRG, etc.	Ultra ISO	EZB Systems, Inc.	http://www.ezbsystems.com	UltraISO is an extremely powerful tool for use with ripping, converting and burning all of the popular image formats. Recommended By RomBomb
CCD + IMG + SUB	Clone CD	Slysoft (aka Elaborate Bytes)	http://www.slysoft.com	Clone CD is no reliable for burning PSX ISO's. You can get rid of the CCD file and just use the IMG and SUB in another program below
NRG	Nero	Nero Inc.	http://www.nero.com	None
MDF/MDS	Alcohol 120%	Alcohol Soft	http://www.alcohol-soft.com	None
DAA	PowerISO	PowerISO Computing	http://www.poweriso.com	None
UIF	MagicISO	MagicISO Inc	http://www.magiciso.com	None