It's happened to all of us - we are in the middle of configuring our L3 switch or router and we can't continue until verifying some other information with a show command. In the past, we would CTRL-Z out of what we were doing, use our show command(s) and then go back into config mode. What a pain!
These days, assuming you are running a current IOS, you can merely use the do command from config mode (or any other submode) in order to run your show commands.
Here is an example from CCO.....
Router(config)# do show interfaces serial 3/0
Serial3/0 is up, line protocol is up
Hardware is M8T-RS232
MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec, rely 255/255, load 1/255
Encapsulation HDLC, loopback not set, keepalive set (10 sec)
Last input never, output 1d17h, output hang never
Last clearing of "show interface" counters never