What are some uses of oxidative/reductive power inside cells?
This topic is quite broad, excluding energetic metabolism, there are still many reactions that use redox equivalents, whether NADH, NADPH, or FADH. Here are some paradigmatic illustrations.

Xenobiotic metabolism


Oxydation of substrate : as you mentioned, alcohol to aldehyde to carboxylic acid. Generate reducing power. (The alkane oxydation shown below occurs in bacteria)





Mono-oxygenation : hydroxylation of a substrate with $O_2$, with the other oxygen atom reduced to water. This proceeds as follow with CYP450 enzymes :





Regeneration of oxided gluthatione



Anabolic metabolism

Basically every time there is a need to create/remove a double bond, or move from carbonyl to aldehyde to alcohol and back, redox equivalent are used.


Fatty acid elongation : as this proceeds with acetyl-CoA as carbon source, intuitively one sees the need to reduce the carbonyl to obtain an alkane chain.





HMG-CoA Reductase (HMGCoAR) catalyses the commited step in cholesterol synthesis.





Synthesis of prostaglandins from arachidonic acid. (More generally, any lipidic mediator)




There are many, many more examples. You may want to check out the Wikipedia page for NADH, NADPH, FADH, or the list of enzyme that use them (1, 2, 3)

All illustrations from Biochemical Pathways, G. Michal &amp; D. Schomburg, 2nd edition, Wiley