IANAL, but the language of this agreement is overly broad. If it is enforceable in the state (or country) where you work (work-for-hire laws vary from state to state (and, obviously, country to country), and in some cases may preclude contractual clauses like this), it would effectively bar you from making any contributions to open-source projects, creating any software of your own, or even posting ideas for software to internet discussion groups without
- those ideas becoming the sole property of the employer, and
- exposing yourself to liability for disclosing the intellectual property of your employer.
I for one would never sign or advise anyone else to sign an agreement this broad, partially because software is my main hobby as well as my job, and mostly because Github Is Your New Resumé.
Most companies that have contacted me with job offers had already found my Github profile, seen my open-source contributions. Many recruiters I talk to at conferences say they would never hire anyone who didn't have significant activity on Github.
If this is a job you are considering, get a lawyer to review the agreement first. If it's for your current employer, look for a new job.
It occurs to me that based on the license, you may be able to contribute patches to existing open-source projects, if that interests you. But I'm pretty sure doing a startup-weekend or hackathon style event and owning the result is impossible if this agreement is indeed binding. Either way, this type of agreement is far too stringent, and certainly not standard. It might have been common decades ago; Steve Wozniak had to offer the original Apple to Hewlett-Packard, where he worked at the time. Luckily, they weren't interested.
Today, this sort of contractual obligation would make it very, very hard for a company to attract good developers. That's something to consider, as well — would you want to work with developers who were willing to sign their every idea over to the company?