I tried everything in this thread without success, but did finally get things working. Here is a summary of my situation:
* Early 2008 Macbook Pro (MacbookPro4,1)
* Was dropped and no longer booted
* Opened it up, disconnected and reconnected everything, no luck
* Purchased new SSD thinking it was a damaged drive (it was not)
* Plugged in new SSD, tried booting while holding Option, drive was not detected
(In between these steps I did countless SMC and NVRAM resets, checked connections, did the tape trick, blew off dust, etc)
At this point I assumed I had a broken hard drive cable. As one last ditch effort, I tried plugging in the old thought-to-be-damaged hard drive into into an external USB SATA dock. To my surprise it was detected by the OS when doing an "Option" boot and I was able to load OS X. From there the OS could see the internal SSD drive I had installed. I formatted the disk (Mac OS Journaled, GUID partition table), downloaded El Captain (newest version that supports that model MBP), and installed it on the internal drive. From there things went smoothly and I now have a working laptop again.
Like I mentioned before, I tried _many_ different things from this thread and others so it's hard to say what exactly got things working again. Hope this helps!