http://www.unbounce.com and http://www.instapaper.com are paid
http://www.launchrock.com is free
Spend all your time optimising the landing page and getting traffic to it, rather than coding one up.
Read these for landing page optimisation
http://unbounce.com/landing-page-articles/the-anatomy-of-a-l...
and
http://unbounce.com/landing-pages/7-elements-of-a-winning-la...
If you're a consumer product then well-targeted facebook ads can drive strong traffic.
http://okdork.com/2014/03/04/how-to-start-advertising-on-fac...
!!Make sure you get the users email address on your landing page!!