Types:

Generic terms and special packaging

CERPACK

Ceramic package

COB (Chip-On-Board)

Bare silicon chip without a package and affixed directly to the circuit board. Use in cost sensitive (ie cheap) applications. Above is probably from a commodity wrist watch. There seem to be two types:

Epoxy blob (below type): die is placed on board, bonded, and then covered with a blob of epoxy. The most common type
Upside down dies (above type): likely WLCSP with underfill. Basically a BGA where there is no encapsulant on the die and solder balls are attached directly to bond pads (see BGA below for example of this sort of thing)
Flexible circuit: these are common in the line drivers on LCD screens

Example showing wire bonding to PCB:

COF (Chip-On-Flex)

A variation of COB, where a chip is mounted directly to a flex circuit

COG (Chip-On-Glass)

A variation of COB, where a chip is mounted directly to a piece of glass - typically an LCD

CSP (Chip Scale Package)

Package no more than 1.2x the size of the silicon chip.

LTCC (Low Temperature Co-fired Ceramic)

???

MCM (Multi-Chip Module)

Several dies integrated into one package. Considerable variety.

Flip chip

A package where the die is mounted upside down. Usually this implies BGA or similar package.

Ceramic BGA example

Had thermal paste to improve conductivity:

After cleaning:

When most solder balls are removed on the bottom looks like this:

After dissolving some of the epoxy on the top:

As can see in above though there was still some underfill left. Next pictures show the epoxy/underfill not completley dissolved and some gunk (solder paste?) left in the center as well as some sort of spacer:

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