In principle yes, but in practice, not really: it'll be a kludge.
If you encrypt only the password, then you may be vulnerable to CSRF attacks. An eavesdropper can still see all the page content, and in particular, if CSRF tokens are included in the link, then the eavesdropper can see all of the CSRF tokens and mount a CSRF attack. It's possible to defend against this with sufficient effort, but it requires still more work on both the client and the server, and is tricky to get right.
If users can log into your site using their Facebook account, since you don't control Facebook, you can't prevent an eavesdropper from stealing their Facebook account and then logging into your site.
You have to be careful that you don't lose the benefit of caching.
Now I'm not saying it's impossible. It almost certainly isn't. It is almost certainly possible to build a web site and a solution that prevents most passive attacks. But it will be complex and non-trivial. That means you'll need considerable security expertise to build it, and there's still a non-trivial chance you screw something up. It also means that the result will be expensive. And the security is inherently limited -- any scheme will be only a partial solution/mitigation -- so the value is limited. I don't think it's a good tradeoff.
If you want to read about state-of-the-art attempts to defend against eavesdropping without use of SSL, here's a great resource for you:
- Ben Adida's SessionLock and http://benlog.com/articles/2010/10/25/keep-your-hands-off-my-session-cookies/
I'd also like to share with you some resources on making SSL perform well:
- EFF's guide on deploying SSL: https://www.eff.org/pages/how-deploy-https-correctly
- Tips from Google on making SSL fast: http://www.imperialviolet.org/2010/06/25/overclocking-ssl.html
- Ivan Ristic's top 10 SSL deployment mistakes: http://ssl.entrust.net/blog/?p=155
- Ben Adida's skepticism, and some replies from users: http://benlog.com/articles/2010/10/26/ok-lets-work-to-make-ssl-easier-for-everyone/
SSL isn't free -- but also keep in mind that people sometimes assume the performance impact of SSL will be worse than it actually is.