I think you can speak in terms of the technology you used, what you liked about it, what you disliked about it, the business objectives and how you helped achieve them and still do fine without showing an actual code repository.
Most interviewers come in with a list of questions they want to ask, so if you can talk about your work in terms of the answers you know they want, you're probably better off than a candidate who can demo a project that the interviewer may or may not care to see.
For keeping a log of what you've done, I don't think there's too much you can do about this. Part of your agreement when being hired is that you are being paid to build something that belongs to your employer. The only way around this I could see is if you were able to extract some abstract tool that could have wider use and get permission to distribute it or at least keep a copy for yourself (a lot of employers won't agree to this, however).
Most interviewers come in with a list of questions they want to ask, so if you can talk about your work in terms of the answers you know they want, you're probably better off than a candidate who can demo a project that the interviewer may or may not care to see.
For keeping a log of what you've done, I don't think there's too much you can do about this. Part of your agreement when being hired is that you are being paid to build something that belongs to your employer. The only way around this I could see is if you were able to extract some abstract tool that could have wider use and get permission to distribute it or at least keep a copy for yourself (a lot of employers won't agree to this, however).