gFTP is a free multithreaded ftp and sftp client for *NIX based machines.
It has the following features: 
  Distributed under the terms of the GNU Public License Agreement 
  Written in C and Can use GTK+ 1.2.x+ or GTK 2.x for the GUI (or text mode)
  Multithreaded to allow for simultaneous downloads 
  File transfer queues to allow for downloading multiple files 
  Supports downloading entire directories and subdirectories 
  Extensive connection manager
  Supports resuming interrupted file transfers 
  Supports caching of remote directory listings 
  Drag-N-Drop support 
  FTP proxy server support 
  Supports connecting to a FTP server via command line parameters.
  Supports associating icons with particular file extensions in the list boxes 
  Sorting capabilities in the file list boxes 
  Can restrict files in the list boxes to a particular file specification 
  Supports viewing and editing of local and remote files 
  Allows for passive and non-passive file transfers 
  Eliminates buffer overruns from malicious ftp sites 

WWW: http://gftp.seul.org/