Random as ****!
* NE555 is old-skool analog timing/cycling that can also be abused as a relay driver or even as a latch.
* UCx84x is a family of SMPS controllers - typically for the primary side of off-line PSUs, or transformer coupled DC-DC applications. They are also pretty long in the tooth but nowhere near as ancient as the 555. There are probably some fringe hobby applications, but otherwise they are pretty much repair parts.
* The 24Cxx I2C EEPROMs are useless without a processor to read them. Sometimes its a MCU you are writing code for, sometimes its OEM firmware or a hardware state machine in some application specific USB IC, or various other applications where storing a tiny amount of data is worth the cost of an extra IC (e.g. monitor EDID).
While you *COULD* (if you are a masochist) use UCx84x if you were designing your own SMPS to power circuits containing the other two, anything with a 555 is *VERY* unlikely to have an I2C EEPROM and visa versa!