Have you read Deathworld (also by Harrison)? There are three books to the set, though I have to agree with Chris that the companion volumes are certainly a drop in quality... still, I did enjoy them when I read them, many, many moons ago....
Also ... Bill, the Galactic Hero is a spoof of Heinlein (and others using those character types) ... quite a good one, I thought.
Some of the early John Brunner might fit your request, though a bit more cerebral they are certainly fast-paced enough; things like
Meeting at Infinity or
Into the Slave Nebula are entertaining quick reads (I'd suggest
The Dreaming Earth as well, though some people are disappointed with the ending).
The following has some good suggestions in the adventure/space opera field:
Space opera - Wikipedia, the free encyclopedia
Just scroll down to the list of books/series at the end of the article proper; and take a look at some of the other links dealing with different types of sf.
You might also look up that rather odd little book, Space War Blues, by Richard A. Lupoff, a "New Wave"-ish sort of space opera, a stylistic tour-de-force that really is worth giving a try.
And there are several of Asimov's earlier sf novels that might appeal:
Pebble in the Sky,
The Stars Like Dust,
The Currents of Space, etc. Quite a lot of things from the Golden Age would fit, both in shorter forms and in novels, i would think, as there was a heavy slant toward adventure, futuristic scenarios, and terse writing (leading to slim books, but often with considerable content in small compass). A. E. Van Vogt may be a good choice, as well, especially something like
The Weapon Shops of Isher,
Voyage of the Space Beagle, and so on. And, if you've not read them, by all means read
The Demolished Man and
The Stars My Destination, by Alfred Bester. These are very fast-paced, and extremely readable, not to mention among the great classics of the genre.