Mini-howto on Flashing Intersil Prism Chipsets: http://linux.junsun.net/intersil-prism/
Most likely you only need Latest-prism.tar.bz2, which contains the latest firmware version of all kind.
If you need a specific version of the firmware, look for archives starting with numbers. The numbers are versions of the secondary firmware. Full collection of primary firmwares is available in primary.tar.bz2. Prism2 based cards use primary firmware version 0.3.0. They don't need primary firmware upgrade.
The naming convention for firmware images is explained in http://home.eunet.cz/jt/wifi/Download.pdf
Use prism2_srec from hostap distribution to check compatibility of the firmware. It should be safe. Please don't ask me what firmware it right for your card. Let prism2_srec find it out for you. If used without switches, prism2_srec only checks compatibility and doesn't load the firmware. If firmware is incompatible, you will see an error message saying so.
Host AP driver for Intersil Prism2/2.5/3 can be downloaded from http://hostap.epitest.fi/
Please note that prism2dl that comes with recent versions of linux-wlan-ng is not as good as prism2_srec at checking compatibility of the firmwares with each other and with the hardware. Use prism2_srec and hostap for flashing to play safe! Don't use any unofficial version of prism2dl - they are extremely unsafe!