I had a "How do I do X?" question, and the answer came in the form of:
I have code that I can share, please contact me.
I got exactly what I needed, at no cost to me. I feel grateful, but I others won't get the benefit exclusively from reading.
EDIT: After the feed back from stackexchange I am not so sure of the following.
I want to clarify that I think is is perfectly acceptable to post an offer to help, and suggest/ask to be contacted by email. There could be many reasons for it, and as a whole these responses do help the Stack Overflow community.