The short answer is I'm not sure there really is a good one to be had...
We use Excel and our spreadsheet is reaching about 15 tabs, most multipage, it only does one method of wind and seismic analysis and it is getting so sensitive that we have strict instructions in the office regarding changes to the sheet.
We have a client who wrote and sells a nice beam program. He spent quite a few hours studying our sheet, talking to his clients and jurisdictions, all with the intent of writing software to perform a lateral analysis on a wood framed structure. He eventually concluded that the market was too small and the "math problem" too complex and dynamic to boil down into a useful program. I believe he also spent a fair amount of time searching for any competing products that may exist in the market place. I don't believe there were any complete packages and he concluded it was likely due to the previously mentioned challenges.
If you know any Plan Reviewers or Building Officials, they may be able to steer you towards a copy of calculations from a good engineer in your area. Green engineering paper is a good place to start along with a copy of "Design of Wood Structures" by Donald Breyer. He is highly regarded on this topic...
If someone knows of something, please let us both know...