You'll see loads with an 8" scope! Even from a suburban backyard, you can find many dozens of interesting objects (as many as half of
John Bambury's list of 600 southern objects with time and practice), and you'll see some great detail in bright objects like Eta Carinae, the Tarantula Nebula and many others. Lots of clusters will be rich with stars, and an 8" will begin to resolve many brighter globular clusters. Views of 47 Tuc and Omega Centauri are spectacular. Saturn will be beautiful, and you should be able to see the Cassini Division on many nights, as well as several moons (up to five?), and occasional details on the planet, like subtle cloud belts will be visible with time at the eyepiece. Ditto for Jupiter - Red Spot, main cloud belts, other cloud features, spots, festoons and barges. You'll have to wait a while for Mars to be big enough for a decent view (it's tiny just now), but once it is, in early 2014, the polar caps and some dark/light features on the planet in good seeing.
If nebulae are going to be your thing, I'd definitely recommend saving and getting a nebula filter (something like a "UHC" or "nebula" filter) - one that fits 1.25" eyepieces is ~$80-$130. In a light-polluted backyard, these work wonders on emission nebulae and planetary nebulae. With this, you'll see over a dozen patches of nebulosity in the Large Magellanic Cloud on a good night, many otherwise invisible details in bright nebulae, and track down fainter nebulae such as Thor's Helmet. Eta Carinae will extend well beyond the field of a low-power eyepiece! From a dark sky the views only get better of course.
From a dark sky, hundreds of galaxies are visible with an 8", but most will be faint puffs and streaks of light. Still, it can be a bit awe-inspiring to appreciate what these little smudges are, and just how many of them are out there. Filters don't tend to work well with galaxies.
So lots to see with an 8", and enough to keep you busy and excited for years
. If you can get up to a 10", the views will be better still!