A general technology conference, but with some good presentations on different tools and their technologies.
LinuxWorld Expo (http://www.linuxworldexpo.com)
Obviously specific to one operating system, but with lots of speakers who are experienced software developers and toolsmiths.
ICSE (http://www.icse-conferences.org)
International Conference on Software Engineering, organized by the ACM and IEEE. Mostly papers from academia, but useful for seeing what ideas other people have already investigated.