All Yamaha receivers have "HDMI passthrough" that allows you to do exactly what you've asked. When you turn the receiver off it sticks with the last source you had selected and passes the signal strait to the TV acting as if the receiver isn't even hooked up. Two drawbacks: you will have to turn the receiver on in order to change your source selection, and this will only work for HDMI sources. I'm sure other brands have this as well, but I am not familiar enough to point them out.
HT: Samsung LN32B460 32" LCD (greyscale calibrated) | AVR: Yamaha RX-V765 | L/R: Emp E55Ti | C: Paradigm Center 1 | Rears: Sony Junk | SW: Klipsch RW-10d miniDSP | Sources: Acer Revo Ion running XBMC with mySQL library server and 4 TB HDD, PS3, Technics SL-Q2 TT | 2x Aura Pro Bass Shakers
Bookshelf: Yamaha RX-V992 | Paradigm Mini Monitors
Shelved for now: Paradigm 11 SE Deluxe