Specific recommendation would depend on what magnification you want, but brand-wise I'd look at Primary Arms, Athlon, and Burris to get the best bang for your buck under $300. There are Leupold, Vortex, etc. scopes in your price range as well, they tend to be a little more basic feature-wise in that range but are solid scopes.
Really, lots of good options in your range just need to know more about specifics as far as what you want (reticle, magnification, fixed vs adjustable parallax, illumination, etc.).
I've personally never spent more than $300 on an optic EXCEPT my night vision (which is a Sightmark Wraith I got for $375) and I've been pretty happy.