(For more informations, you can also read this old article.)
I finally had time to use my Saturn, and I could verify that iso/cue "loader" works on real hardware !
Of course it works well when reading from RomFs, and it works also well when reading file from SD card 
My test environment ... sorry for the mess 
(Micro SD card is located on top-left of the cartridge)
I lost some time to understand why data transfer from SD card was slower than expected, but finally understand why : some debug/whatever delay routine was called when accessing cartridge registers ...
Just putting some #if 0 around this delay code solved the "problem" ^^;
Read more Iso/Cue "loader" works on real hardware :]
So I am making an enhanced version of Pseudo Saturn firmware.
And, as an extra feature of this firmware, I added an iso/cue "loader".

Why the quotes around "loader" ? Because it doesn't emulates CD-block

So, it only loads few homebrew games, but it's enough for me, and I don't want to waste more time on adding CD block software emulator while better solutions (rhea, jhl's "mpeg" cart, etc) already exist.
As an other bonus, I also added RomFs support to my Saturn library

It is like romdiskfs that is widely used on linux, DS homebrew, etc, but it allows file compression, some other features, and ... is probably buggy because I coded it from scratch

(*) Virtual file system is not really new on Saturn homebrew scene, because Piratero already implemented one in libyaul a while ago

RomFs root folder contents. I will load sl_elf.iso file in the next paragraph.
So here is a capture of yabause running sl_elf.iso, after decompressing it from virtual file system stored in Flash memory.
sl_elf.iso is "satdemo" made by CharlesDoty, grabbed from SaturnOrbit's examples (Thank you Rockin'B for making SaturnOrbit ! After 10 years, it still have it installed on my laptop's hard disk

).
yabause running Saturn demo from iso file, near SatLink software I use in order to debug my Saturn programs.Very big thanks to the yabause team ! I grabbed the iso/cue loading routines from yabause sources, and it was very easy to port them

Edit : I removed unused code (CD Block emulation routines, etc) from iso loader module, and .o size dropped from 74KB to 18KB oO
Edit (2015/06/26) : I tested this code on real hardware, and it works too ! Please see
this article for more details.
Read more Iso/Cue "loader" works :)
After making some cleanup in my development folders, I found an old archive file 
It is dated 2007 June 20, and contains a very early version of ietx2, which is an adaptation of yeti3D engine to Saturn.
At that time, I was using a PentiumIV processor and 80GB IDE hard disk in order to run sh-elf-gcc provided by SaturnOrbit ... very nostalgic times ... but I definitely prefer nowadays for Saturn development 
Iso file can be found >>> here <<<.
(No, there are no sources available, because I didn't kept archives of sources at that time.)
Please don't waste a CD-R for this. You can try on yabause, or just look at screenshot and say "hey, very ugly stuff" however.
ietx2 beta screenshot : not enough time to draw last quads in VDP1 list, hence the garbage on foreground.
ietx2 beta screenshot : example of incorrect rendering when quads coordinates exceed 16 bits range.Present version
You can find current version (ietx2) and sources of my Yeti3D adaptation
here (dated 2011 April 19).
Also, there are videos of ietx2 available below. Click on the links to display them on youtube.
Future (?) version
I'm still maintaining sources of ietx2.
I renamed project name to ietx3 (yeah, I'm not very original when choosing project names

), and now use a lite version of Yeti3D PRO engine ... "lite" means original, minus a lot of features, in order to keep a decent frame rate, and fitting to Saturn resources.
You can find some videos (binaries are not released, sorry) on my youtube channel :
Read more Nostalgia time : ietx2 old (buggy) beta iso for download
So I'm currently making a Saturn Backup Data Manager utility.
What's this ? It is a remake of "Memory Manager" utility present in Saturn BIOS.
Sega Memory Manager utility : main screen
It already exists, and can be used from BIOS, so why making such an utility ?
I have some reasons that pushed me making this, and one of theses is that Memory Manager user interface is very cheap, especially, it doesn't allows to select multiple backup data and copy/delete them. (Dear Sega, why didn't you developed this feature ??)
Also, there are some new features I would like to add, such as hex-edit of memory data ... I have very few time to play now (real life, children, cancer, etc), so 999 lives in Backup data is a must-have feature 
This utility is currently WIP, so no download link is available right now, but it is WIP enough to publish screens on my blog 
So here is what it looks like now :
Backup Data Manager Main Screen
Don't trust the development progress only by looking at the main menu : everything behind is far for being finished 
But at least, menu library itself is more or less completed, and I'm very glad about this point.
Here is a comparison of data selection screens :
Data Selection (Sega)
Data Selection (this utility)
Yeah, I know that Japanese text is not displaying properly ... this will be fixed, but the priority for this is low, so please be patient.
And what is the green text display on Backup Data Manager screen ? This is multiple items selection 
As a bonus, here are screens of Backup Manager running on real hardware.
Pictures were taken last September, when I still had a modchipped Saturn ready for use ... after that I was busy with medical stuff, and moving to a new apartment, so my Saturn I used for testing is currently hidden in a cardboard ...
Early version of Backup Manager, picture was taken 4 months ago.
Can you spot the differences with current version ? ^^
SatLink running on my 8 years old laptop, connected to my Saturn via USB dev cart.
This development environment is by faaar more convenient than $500+ vintage
development hardware/carts/whatever floating on ebay ♪
Among the things I would like to add before a release, there is the Saturn FDD support ... but I don't own Saturn FDD unit, and the cheapest unit I could find on auction sites costs 10'000 Yens, and the seller doesn't guarantee that it still works ...
I won't pay 10K Yens for a vintage objet I will only use once a year (and I fear my wife would trash it if she founds it
), so if somebody is ready to give some time for beta testing with Saturn Floppy Disk Drive, please let me know in the comments 
Read more Backup Manager - Early Version #1