We found this great howto on smbjorklund.no
"This howto will show you how to get those pesky PECL modules to compile in MAMP like uploadprogress or Xdebug. First a little Drupal background information. FileField and ImageField 3.0 for Drupal 6 released as one of many new features enables us to use the PHP extension uploadprogress that especially come in handy giving the user feedback of progress when uploading large files. Many OS X users are using MAMP to sandbox their development environment but compiling a PECL/PEAR module is not quite that easy in MAMP."
Read the the whole article right here at http://smbjorklund.no