You might want to take a seat for this one: an early Gingerbread build has leaked for the Samsung Galaxy S I9000, and is now available for download. The file first landed in the hands of one Tricky103, and shortly thereafter was downloaded from Samsung's internal database and uploaded to a public mirror courtesy of iammodo.
Installation instructions are
virtually non-existent in the post, so you should probably know your way around modding already before attempting this (update) turns out installation instructions aren't there because it's super simple: just use the three button combo to flash the new ROM. Beware, though, as rumor has it that Samsung is moving towards locked bootloaders, and so our gracious leakers have provided two versions of the ROM. The first comes with, and the second without, the bootloader. About all the further details they provide:
Flash with out pit and with no repartition, or with any pit and repartition if you want to change pit.
Upload works VOL up+Power+Home
download work VOL down+Power+Home
They've mirrored the files to MultiUpload; you can click here to download the version with bootloader, or here for the version without. Beyond that, details are incredibly light at the moment. I've gone through the first 20 pages of the thread and aside from ultra-brief (1-2 sentence) follow-up posts from iammodo, there isn't much to this yet (as far as details, installation instructions, etc.) that I've found.
If you take the dive (and at this point, I'd again stress that you shouldn't unless you know what you're doing), let us know how it goes. If you spot detailed instructions, more pictures, details, and so on, feel free to drop us a comment line below (and a source link, if applicable), and we'll update accordingly.
As always, any questions about installation or other requests for support should be directed to the source thread, as they're far more capable of helping.
[Source: XDA Developers]