Hi, GDB lacks UI. and linux is not integrated yet. 

http://www.gnu.org/software/ddd/
http://cgdb.sourceforge.net/
http://www.newplanetsoftware.com/medic/
http://members.nextra.at/johsixt/kdbg.html

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http://www.elis.ugent.be/diota/
http://www.cs.man.ac.uk/~brejc8/kmd/index.html
http://lcamtuf.coredump.cx/soft/memfetch.tgz (12kb)

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http://www-124.ibm.com/developerworks/oss/linux/projects/dprobes/
http://www.opersys.com/LTT/
http://www.jungo.com/dnload.html ($)

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http://www.nongnu.org/guss/
http://hpclab.cs.tsinghua.edu.cn/~skyeye/eng/index.html


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PS:  objdump/binutils, strace
http://www.devchannel.org/article.pl?sid=03/10/24/2057246
Thanks to freshmeat.net, OSnews.com