Too many to list in one post. Here are a few benchmarks (one-way distances):
Hoboken waterfront (train station to 14) assuming you hug the river: 1.5 miles.
Observer to 14 (on Garden for example): 1.2 miles.
Church sqr park (CSP) to port imperial ferry: 2.5
CSP to Jacobs Ferry (expensive condos where the driving range used to be): 4 miles.
CSP to North Hudson Park 5-6 miles.
CSP to Circle K store in Edgewater: 8.
CSP to GWB: 10.
CSP to GWB to Bwy to Central Park to 34th Street PATH: 20.
There's also the viaduct up to Union City/JC Heights. THe JC waterfront is changed in a HUGE way - don't want to miss that.
Or you can do endless loops around town. That gets old quick.