The log shows missing symbols:
Undefined symbols for architecture x86_64:
"boost::system::generic_category()", referenced from:
global constructors keyed to _ZN12_GLOBAL__N_12_1Ein mapnik_datasource.os
global constructors keyed to _ZN12_GLOBAL__N_12_1Ein mapnik_datasource_cache.os
global constructors keyed to _ZN12_GLOBAL__N_12_1Ein mapnik_feature.os
global constructors keyed to _ZN12_GLOBAL__N_12_1Ein mapnik_featureset.os
global constructors keyed to _ZN12_GLOBAL__N_12_1Ein mapnik_filter.os
global constructors keyed to _ZN12_GLOBAL__N_12_1Ein mapnik_font_engine.os
global constructors keyed to _ZN12_GLOBAL__N_12_1Ein mapnik_geometry.os
...
"boost::system::system_category()", referenced from:
global constructors keyed to _ZN12_GLOBAL__N_12_1Ein mapnik_datasource.os
global constructors keyed to _ZN12_GLOBAL__N_12_1Ein mapnik_datasource_cache.os
boost::mutex::mutex()in mapnik_datasource_cache.os
boost::mutex::lock() in mapnik_datasource_cache.os
boost::unique_lock<boost::mutex>::lock() in mapnik_datasource_cache.os
global constructors keyed to _ZN12_GLOBAL__N_12_1Ein mapnik_feature.os
global constructors keyed to _ZN12_GLOBAL__N_12_1Ein mapnik_featureset.os
...
ld: symbol(s) not found for architecture x86_64
This could be an incompatibility with boost 1.50, to which the boost port was recently updated; we've seen such incompatibilities in other ports and it's not uncommon for new boost versions to break other ports. You could try downgrading to boost 1.49.
However, before you do so, note that the log also says:
DEBUG: Skipping completed org.macports.archivefetch (py26-mapnik)
DEBUG: Privilege de-escalation not attempted as not running as root.
DEBUG: Skipping completed org.macports.fetch (py26-mapnik)
DEBUG: Privilege de-escalation not attempted as not running as root.
DEBUG: Skipping completed org.macports.checksum (py26-mapnik)
DEBUG: Privilege de-escalation not attempted as not running as root.
DEBUG: Skipping completed org.macports.extract (py26-mapnik)
DEBUG: Privilege de-escalation not attempted as not running as root.
DEBUG: Skipping completed org.macports.patch (py26-mapnik)
DEBUG: Privilege de-escalation not attempted as not running as root.
DEBUG: Skipping completed org.macports.configure (py26-mapnik)
DEBUG: Privilege de-escalation not attempted as not running as root.
The "Skipping completed" lines show that you had not cleaned before trying this build, so its results cannot be trusted. Please "sudo port clean py26-mapnik" and then try again. If it still fails with undefined symbols, then proceed as above.
