I have a cool "addon" which isn't actually an extension - it's a bookmark that I've got which uses Javascript.
It allows you to save any password, even if it's set to not allow (like for your banks website)
Code:
javascript:(function(){var%20ca,cea,cs,df,dfe,i,j,x,y;function%20n(i,what){return%20i+"%20"+what+((i==1)?"":"s")}ca=cea=cs=0;df=document.forms;for(i=0;i<df.length;++i){x=df[i];dfe=x.elements;if(x.onsubmit){x.onsubmit="";++cs;}if(x.attributes["autocomplete"]){x.attributes["autocomplete"].value="on";++ca;}for(j=0;j<dfe.length;++j){y=dfe[j];if(y.attributes["autocomplete"]){y.attributes["autocomplete"].value="on";++cea;}}}alert("Removed%20autocomplete=off%20from%20"+n(ca,"form")+"%20and%20from%20"+n(cea,"form%20element")+",%20and%20removed%20onsubmit%20from%20"+n(cs,"form")+".%20After%20you%20type%20your%20password%20and%20submit%20the%20form,%20the%20browser%20will%20offer%20to%20remember%20your%20password.")})();
Just cut and paste that into a bookmark and when you're on the login page for your bank (or whoever) click on the bookmark and you'll get a pop up.
Ediit;
Nevermind it looks like it won't "read" properly on here....