Being no spring chicken, I've stumbled upon - and used - a number of marketing tools throughout my career. Below are my favorites, and each comes with an extremely high recommendation from me. If you have any questions, just ask.
My buddy and fellow Marketo Champion Joe keeps a marketing blog, too, and he's seriously better at it than I am. Go here if you want a bunch of Marketo goodness, how-to videos, and the more-than-occasional Star Wars reference.
If you're using Marketo and haven't checked out Josh's Marketing Rockstar Guides, then you're missing out (and probably not using Marketo to its full capabilities). Make sure to subscribe to his updates for a free download you'll want to add to your marketing toolkit.
This site is relatively new, but I have so much faith in what it's about to do for marketing that I thought it deserved recognition. Submit your landing page for feedback or join to critique others'. Best of all, it's FREE. You no longer have an excuse for not testing your message and CTAs.
On top of being a premiere landing page solution for marketers (read: no coding required), Unbounce offers incomparably valuable webinars and blog posts that will fast-track your conversion marketing.
My favorite marketing automation tool. Reasonably priced for SMBs looking to do more than basic lead management and email marketing. Even the entry-level analytics are essential for making marketing decisions that impact revenue, too (although I recommend getting the biggest analytics your budget allows for).