Why polymeric solids are said to be intermediate between crystalline solids and amorphous solids? Crystalline solids have ordered arrangement and amorphous solids do not. Polymeric solids are simply formed by the joining of some monomeric units. It has nothing to do with ordered or not ordered then why they are called intermediates.
 A: A general highly simplified overview:
Generally macromolecules/polymers exhibit very complex structures. The completely disordered/amorphous state is on the one hand to be expected from purely configurational entropy considerations, on the other hand there are cases where the chains or side-chains would energetically favor to be aligned, but this can almost never be fully achieved as polymers tend to form networks, by getting entangled onto one another (e.g. covalently, thus very robust networks can result). Thus the emergent properties of a mixture of polymers in a frozen state will generally lie between that of the crystalline and amorphous solids, where some regions are semi-crystalline, some amorphous. See e.g. this schematic drawing from wikipedia: ("Spherulite2" by Materialscientist - Own work (transfer my upload from en.wiki). Licensed under CC BY-SA 3.0 via Commons)

Note that alignment of side chains does not always come with entropy reduction, rather often it leads to more efficient packing of the chains, thus leading to higher rotational/translational mobility, where the effects of topological limitations are minimized. There are many other factors that play important/competing roles, e.g. the boundary attraction, solvent properties, homogeneity in number density distribution of monomers, and so on. All of which means that at the end, through free energy minimization, highly non-trivial equilibrium structures will emerge.
A: Polymers come in many different shapes and forms in terms being crystalline or amorphous.
Broadly speaking we can categorise them as follows.
1. Semi-crystalline thermoplastic polymers: like polyethylene (PE). Extremely high Molecular Mass (100,000 and higher) make these very long strands difficult to align into crystallites. Relatively small areas in the polymer nonetheless do form crystallites and these greatly contribute to mechanical strength (stiffness) of the material. High density PE (HDPE) has a higher overall crystallinity than low density PE (LDPE) and the former is correspondingly stiffer than the latter.
2. Fully amorphous thermoplastic polymers: like polystyrene (PS). PS is a 'glassy' polymer that is fully amorphous but with a Glass Transition Temperature ($T_g$) of about $100^\circ \text{Celsius}$. Above this temperature the strands regain their mobility and PS starts 'melting' at that temperature.
3. Fully amorphous elastomeric polymers with low $T_g$: like natural rubber (NR, polyisoprene). Fully amorphous NR has a very low $T_g$ (typically about $-80^\circ \text{Celsius}$) which allows the material to retain its rubbery, elastic properties from room temperature (and above), down to about $-80^\circ \text{Celsius}$. In addition, some synthetic amorphous rubber polymers may also have some built-in crystallites to improve mechanical strength.
