Each of these increase the number of HP you get back during a rest.
The Healthful Rest spell description (SC, p. 11) says:
Each affected creature regains twice the hit points and ability damage it otherwise would have regained during that day, depending on its activity level
The Summon Elysian Thrush spell description (SC, p. 214) says:
Those within 30 feet who listen to the thrush's song while resting recover at twice the normal natural healing rate.
The description of the Magic Bedroll (MIC, p. 163) says:
After sleeping for 8 hours in the bedroll, you recover 1 hit point per character level, in addition to the hit points you recover normally.
If I sleep 8 hours in a Magic Bedroll while listening to an Elysian Thrush, and under the effect of Healthful Rest, how many HP do I regain?