Good intellectual property lawyers are more spendy than you would wish, so consider carefully the upside of getting good legal advice versus the downside of flying without it. Depending on what you are developing, subject matter knowledge may be important, and that is often better found in a specialty intellectual property firm rather than in the intellectual property section of a general practice law firm. But if your main concern is making sure your agreement with your employer properly separates the rights in his project and the rights in yours, then you may as well seek a general practice law firm, because then what you are looking at is contract law (and the possibility or not of future litigation) as much as intellectual property law proper.

Perhaps a labor lawyer, rather than a general contract lawyer. The main thing on your part is that you dont use your employer's IP, time, equipment, or work space. IANAL. Ask the lawyer about this area of expertise, otherise you pay $400/hour for him to learn.

I discussed all of this with them and I have been very careful to only develop (or even read articles) on my machine and reserve theirs for semantic technology work. I don't feel anything antagonistic at this point, but I would like to at least understand what I am risking.

That makes a lot of sense, thanks. Do you know how I would find a decent firm for this? Are there any good review sites? Are we talking $500? $1000? more? Just a general idea...