The idea that you can pick from many lead capture options that are free is a loaded idea.
What I mean is, yes there are many free lead capture software options but you may be better off paying for something because it will look more professional and you can count on it a bit more.
One of my favorite free lead capture tools is Google Docs, as long as you do not mind it being branded by Google Docs and you are not looking for anything other than capturing the lead information. You just choose the “forms” option and Google docs will build your a form, embed script to add it to your website and a Spreadsheet to capture the data. I always set it to email me whenever the form is updates so that I know when I generate a lead.
Next would be the many WordPress lead capture plugins (search forms) that you can find. My advice here is to test carefully and retest often. All too often I have done an update on WordPress or on a plugin and then gone months not realizing that the form was no longer working. It is a free lead capture option but I never really trust it.
Next would be to use a Free CRM like Sugar CRM. This is not for the faint of heart as setting it up and configuring it can take some tech skills, but these tools, vTiger is another, also will give you free lead capture and an actual system for moving the lead through the sales process.
Lastly, you can use a low cost option like aWeber where you can capture the lead and set up automatic responses to them, as many as you want for as long as you want. This is very effective at generating leads and is a great low cost lead capture option. You can also get something like SalesForce.com or Zoho CRM and it will cost more, but they have support and reliable sales lead capture services.