I got this working and here were the additional steps (Mathematica 8.0 and 
MacOS 10.6.6 -- install Python 2.7, copy 
/Applications/Mathematica.app/SystemFiles/Links/MathLink/DeveloperKit/CompilerAd
ditions/mathlink.framework to /Library/Frameworks, add "-framework 
CoreFoundation" to list of libraries in Makefile

I tried what  yarosla said (copy mlink framework and add -framework 
CoreFoundation in the makefile) with Python 2.6, Mathematica 8.0 and MacOS 
10.5.8.
I still can't compile Pythonilka -first of all, I don't have any libML.a in 
${CADDSDIR}, I have instead a libMLi3.a so I modified the makefile accordingly. 
But I get have a lot of Undefined Symbols during the compilation:
Undefined symbols:
  "std::basic_ostream<char, std::char_traits<char> >& std::operator<< <std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char)", referenced from:
      MLNetwork::MLAddress::WriteAddress(std::basic_ostream<char, std::char_traits<char> >&) constin libMLi3.a(mladdress.cpp.o)
      MLNumerics::MLBigInteger::printcore(std::basic_ostream<char, std::char_traits<char> >&) constin libMLi3.a(mlbiginteger.cpp.o)

 [SNIP]

ld: symbol(s) not found
collect2: ld returned 1 exit status
make: *** [Pythonika] Error 1

Any suggestions?

I couldn't compile with Python 2.6 because it had a different architecture from 
Mathlink library ("file 
/Applications/Mathematica.app/SystemFiles/Links/MathLink/DeveloperKit/CompilerAd
ditions/mathlink.framework/mathlink says "x86_64", but "file <pythonbinary>" 
didn't mention this architecture). Upgrading to Python 2.7 fixed it. However, 
you don't have "wrong archecture message", perhaps you should add "-lstdc++" 
flag in addition to "-frameworks CoreFoundation", as suggested at 
http://stackoverflow.com/questions/5161006/compiling-pythonika-on-macos. Note, 
I upgraded Python through official package rather than MacPorts, MacPorts puts 
it into different location which doesn't get found by default.

@yarosla: Thank's it worked on this machine. Actually both archs for mathlink 
and `which python` match, but i'll keep in mind since i'll be compiling it on 
other machines.
Thanks for the help.  

[OT]: i was wandering: why Pythonika's sources aren't available in the Download 
page?

The thread in Stackoverflow already gives the solution to compiling the 
Pythonika for Mathematica 8. I've added the "-framework CoreFoundation" to the 
Makefile.osx so it should build as expected.

Regarding the availability of Pythonika's sources, they've always been in the 
Google Code's subversion:

http://code.google.com/p/pythonika/source/browse/#svn%2Ftrunk

Dear All, I would love to use Pythonika for Mathematica 8 on my Mac but I have 
very little experience compiling things  This thread is rather intimidating.  
When I attempt to install "Pythonika-Mathematica8-Python2.6" on my Mac I get 
the following error message: LinkOpen::linke: Specified file is not a MathLink 
executable.  As I understand it, the problem can be cured by recompiling 
Pythonika with certain flags.  That's great, but might it be possible for 
someone to post a pre-compiled version that will actually run on Mathematica 8. 
 I loved Pythonika on earlier versions of Mathematica and would like to use 
Natural Language Toolkit again from within Mathematica, but unless I summon up 
the courage to do some compilation, I will be blocked.  Can someone post a 
working executable for OSX 10.7  and Mathematica 8 Version 8.0.1 or above.  
Thanks so much. SJC