Packt has a wide variety of tech books, but editing quality varies.
Same with Apress. Apress has books at $9.99 during Cyber Monday. They are probably the two alternative publishers to consider most similar in scope to Oreilly.
The O'Reilly Learning library includes many Apress and Packt (pretty sure on this one) books. It's not just O'Reilly's own books. It's a pretty massive legal library of technical books, but I don't pay for it myself (my employer pays for it).