“Give me FIVE!" – A QRP SSB multiband transceiver by DK7IH
Building a multi band rig is, as you might conceive, much more complicated than setting up a monobander. Seems sensible.
https://radiotransmitter.wordpress.com/2015/12/08/gimme-five-a-qrp-ssb-transceiver-for-5-bands-with-10-watts-output-power/

A QRP SSB Transceiver by WB9IPA
After having been substantially inactive for the last several years, I decided to get back into amateur radio. Having always preferred tinkering with radios over operating them, I decided ... to build a radio ...
http://www.qsl.net/wb9ipa/Gen1.htm

An experimental DSB/CW QRP rig for 20 and 40 meter bands by IK3OIL
The building of an HF phone rig today isn't shurely a simple job, however I'd like to propose an easy-tomake project, suited for portable or emergency use.
http://www.ik3oil.it/_private/QRP%20sperimentale%20in%20DSB_eng.pdf

Direct Conversion HF Transceiver with DDS LO by OH7SV & OH2NLT
Direct conversion HF radio with DDS frequency synthesizer is very interesting concept. OH7SV and OH2NLT are experimenting with such rig. Full stories will become available when project matures. Here we have some preview pictures and material.
http://www.saunalahti.fi/hohtola/ham/DC-TRCVR/DCradio.htm

Four Band CW Transceiver by PA2OHH
The performance of the 80 meter CW transceiver using the phase method for side band suppression is very good. Construction was easy with all good obtainable standard electronic components ...
http://www.qsl.net/pa2ohh/99trx.htm

HF Transceiver by EI9GQ
This page will describe the construction of a multi band SSB transceiver. Because I do 99% of my operating on my four favourite bands, I decided to build a four band rig with provision for adding a fifth band later.
http://homepage.eircom.net/~ei9gq/rig.html

High Performance HF Transceiver by YO3DAC/VA3IUL
High Performance HF Transceiver.
http://www.qsl.net/va3iul/High_Performance_HF_Transceiver/high_performance_hf_transceiver.htm
 

Home brew HF SSB transceiver by VK3EPW
I responded a CQ call on 14.160MHz today and ended up having an entertaining conversation with Peter, VK3EPW. He's 1,000Km away, was running 15W and using a home made transceiver, so naturally I asked for more information.
http://blog.marxy.org/2008/12/home-brew-20m-ssb-transceiver-by-vk3epw.html

Home-Made KW-Transceiver durch DC4KU
Prinzipaufbau eines großsignalfesten KW-Transceivers mit hochliegender 1. ZF.
http://www.dc4ku.darc.de/KW_Transceiver.pdf
 

Minima -A general coverage transceiver by VU2ESE
The Minima is a simple and easy to operate transceiver for all the HF bands with a crisp receiver, a clean output and component cost of less than $100.
http://www.phonestack.com/farhan/minima.html

Multiband shortwave tranceiver by PE1JPD
During the spring 2013 I decided to build a shortwave transceiver to participate in the vacation round on 40meters. First with 15W only on 40 meters, and with an open dipole on the camping 3 meters above ground I worked a lot of stations in all of Europe.
http://www.pe1jpd.nl/index.php/mutiband-shortwave-trx/

SPOTTO - A Direct Conversion High Performance Universal DSB Transceiver by KANG. K.P.S.
When I incepted the design of SPOTTO the focus was mainly on a simple and quieter high performance receiver with excellent sensitivity and dynamic performance combined with a simple DSB transmitter offering cleanest and moderate output for QRP use.
http://www.hamradio.in/circuits/spotto.php