Updated in December, 2017
My recommendations from last year, largely remain. With regularly priced products, look at Sightron S1, or wait for sales.
Updated in April, 2016
Generally, my recommendaitnos tend to change somewhat every year as new scopes are introduced. However, in the <$150 range, you are still on a pretty severe budget and your options are more or less the same as they were five years ago.
The general notions of going for scopes that concentrate on the basics definitely hold.
In the last few years I spent most of my time on scopes that are a bit more expensive than this category, but I still pay attention to what is out there since I am routinely asked about this.
Most Chinese made scopes in this price range are not my cup of tea. Higher end Chinese scopes got a lot better in the last few years, but in the $150 range, there are still too many QC issue with them.
Hence, most of what I recommend here hails from Phillipines where their QC seems quite good on scopes in this price range. In terms of product lines, look at Sightron S1, Burris Fullfield II, Weaver Classic and Vortex Diamondback.
These product lines have been in production with minimal changes for quite some time, so all the kinks have been worked out and they have made a lot of them, which bodes well for quality.
As far as actual models go, pick the one with the reticle that appeals most to you. Keep in mind that most of these sell for a bit more than $150, but I see them on sale for less often enough. Still, in terms of “regularly under $150” SIghtron’s S1 line-up is your only legitimate option.
To be honest, there is a lot to be said in favor of simple fixed power scopes like Weaver’s Classic K 4×38 and Classic Rimfire 4×28.
With variables, look at the tweener 2-7×35 models form Burris and Vortex.
If I was pressed to the wall to pick one general purpose scope for around $150, I would get this.
Updated in February, 2011
In the <$150 range, you are still on a pretty severe budget with this project. However, your options open up a little bit.
The general notions of going for scopes that concentrate on the basics still hold.
Here are the scopes I (kinda) like in this market segment. Please note, that I am not recommending any scopes with magnification above 9x. However, there is now a decent low range variables and a tweener.
Sightron S1 3-9×40 with #4 reticle (this is probably my overall pick in this category along with the Burris)
Weaver V3 1-3×20
Weaver Classic K 4×38 and 6×38
For rimfire rifles:
Weaver Rimfire 2.5-7×28 is a great little scope as is the 4×28