** NOTE: Sorry if I state the obvious in this post, I'm not sure of you familiarity with Common Lisp**
Carrying on from sds:
There does seem to be a bit of life on getting clozure running on android but the performance available remains to be seen. It is very unlikely that we will get to see lisp games in the iphone store unless they compile to some other language where the compiler is not available at runtime (See Nu or for a proprietary option see mocl which both have ways of addressing this issue)
Portability - Across Implementations
In libraries it is definitely worth while to get them working portably across as many implementations as possible, however for games I'd really just pick one implementation and hone your code on there. You will probably be distributing your game as a package for each platform as opposed to through quicklisp right?
Portability - Across Platforms
Do make sure to check out the progress of you preferred implementation on each platform, there can be subtle gotchas. For me I use SBCL and under Windows only 32bit is fully supported, whilst 64 is still under development.
Packaging
This has some good timing for you as some information on packaging Clozure apps for Apple Mac Store was posted on openmcl-devel today . I haven't had a good read yet but the thread may provide more info.
Zach Beane has also made buildapp for SBCL
The lispbuilder folks also seem to have some info on making standalone executables.
Tools
cl-opengl is a very good wrapper for opengl. It supports both old and modern opengl styles and so I find the areas which try to provide higher level abstractions a bit limiting (I personally steer clear of cl-opengl's gl-arrays). Do have a read of the source though as the is some great stuff there, especially when you start writing more cffi code.
{cl-opengl is still being developed and available through quicklisp - I have used it under linux and windows happily}
lispbuilder-sdl is very cool but again you may find the urge to take control of some areas. For example the sdl:with-events macro is great, but takes control of your main loop and time-step handling. This may work perfectly for you but if not don't be afraid to dig around and write something better to replace those parts!
Also lispbuilder provides a range of libraries so before using them check if there is a more recent equivalent in quicklisp. For example lispbuilder has lispbuilder-opengl. Don’t use this, stick with cl-opengl. Again lispbuilder has lispbuilder-regex while it is probably much better to use CL-PPCRE.
I probably wouldn't recommend use it as it stands but I spent a little time a while back stripping out all of lispbuilder-sdl that didn’t pertain to modern opengl games (so no sdl software surfaces etc). I DON’T think people should use this yet but it may give you some ideas! {lispbuilder isn't under heavy development but is available through quicklisp - I have used it under linux and windows happily}
Also whilst I am pimping code written by great people and then torn apart by me, see this video on how to recompile parts of your game whilst it is running. It is not my technique but does work very well.
The above will require you to be using SLIME or SLIMV which means using either Vim or Emacs. SLIME is really worth your time so do have a look!
All in all, good luck, common lisp is great fun to develop on and while you may find it takes a while to get an opengl work-flow you enjoy, if you have the time I have no doubt you will have a great time.
Look forward to seeing the game!