I have been looking at doing the same and listing the resources with links or in a Wiki style page. Especially those brands where the discontinued models mean the vendors are giving the programming software away.
To add to that list:
They are "discontinued" by Motorola, but found CHEAP. I bought two, each with two batteries, for $120. Programming CAN be done through a $20 cable, and the CE-142 (7-segment model CPS) and CE-151 (dot matrix LCD CPS) are give-aways from Vertex/Motorola.
BE WARNED: Many of them were programmed with the US version CPS which means they are LOCKED narrowband. You CAN reverse that - but be prepared to spend $120 in the Vertex "Flash cable adapter", or find someone (like me) that has one now.
Discontinued by Motorola long ago - almost "throw away radios". Can find them "ready to go" off eBay for $40-50 all day long. Especially if you buy the 450-512 split which is "undesirable" to many.
Cable can be bought from bluemax49ers or other places for around $20, CPS is readily available free.
LIMITATION: Can only program on a 32-bit version of Windows. If you don't have a physical serial port, you need SPECIFICALLY a FTDI branded chipset USB-serial adapter.
Discontinued by Motorola - coming down in price rapidly. These are tanks just like the MTS series - I mean not only "duty ready" but can double as a weapon. Can find them for around $75-$125 if you hunt around. CPS again is readily available free... and uses the same cable as the MTS.
LIMITATION: same as the MTS
Takes same accessories as the last 2 Motorola series - down to chargers in some instances. Requires a different programming cable - but again a serial cable and USB adapter is found by the eBay vendor mentioned in previous posts for $50. They are SOLID radios, bit more flexible programming and features, and can program up on a 64-bit Windows computer. They are MUCH more expensive - creeping into XPR7550 territory... $250+ with some fresh looking ones easily fetching $700. This is where I will put the limit of a GMRS radio - because they are inanely expensive for the purpose.
GREAT TRBO radio, "first generation". Lacking some of the audio enhancements and niceties of the "second generation" XPR7550 - but those limitations are mostly on the DMR side of the radio, and even then are still awesome radios. Can find them for around $200 if you look hard. CPS is pricey - $169 for a 3-year subscription. If you have a friend paying for the subscription that can program for you - you are SOLID. They're a bit more fragile feeling than the MTS/XTS series but I can confirm they will take a beating.
Vertex VX/VX-P 820/920 series
Awesome radios for the price and featureset. the "P" is P25 versions, others are analog. The 820 is my personal favorite - literally a pocket sized public safety radio. My VX-P820 stands at literally half the height of my MTS2000. They can creep up in price - but again free CPS, cheap cables, and parts support via Motorola for a few more years... as parts are available.
I will post some mobiles and other brands. But really... there's a ton to go through. I just chose to mention ones that I have personally used or owned, that were not mentioned yet.
Also a feature to mention with the Motorola line (XTS specifically) - if you buy one with a display and keypad (Model 2 or 3) - you can set the MPL list which stands for "Multiple PL". In my experience, I have all my general use repeaters in my radio for the areas I know I travel. I then have a zone with the "general GMRS" frequencies. I enable MPL on that zone, and set the default PL to 141.3 with CSQ receive. If you know you're traveling and don't want to constantly read/write your radio on a computer - you can just look up online and say "Hmmm this uses PL or DPL XYZ", hit the MPL button, browse to that entry, select. Boom - you're "programmed" for that repeater now. Caveat is MPL means you need to program EACH PL setting you want. If you want them - message me. I have a "sanitized" codeplug with all standard PLs and some common DPLs all done - all you have to do is drag-and-drop.