If you want your sites to rank well in the search engines, then you're going to need to get plenty of one way backlinks from other sites to yours. This is a very time consuming effort and so every tool you can use to automate this will save you time that can be spent on other things like making more sites. To help you on your way, I've listed a few products below that I use in my backlinks building strategy.
If you're going to spend money on one tool, Unique Article Wizard would be the one to spend it on. Quite simply, you write a 400+ word, 5 paragraph article and then 2 more variations of each title and paragraph. You also prepare some different "resource" boxes that contains a backlink or two to your sites, making sure to use appropriate keywords as anchor text. The next step is to submit all that information to Unique Article Wizard (UAW) and once it's approved, they will combine those different paragraphs to form a somewhat unique article and blast it out to various article directories, blogs and more. All you have to do is sit back and wait as you get 100s of backlinks back to your sites for just an hour of work if that! Every day I write at least one new article and use this tool to blast it out and garner all those content and keyword rich backlinks. At the time of writing, this tool only costs $67 a month and as I said, if you're going to spend money on any tools, Unique Article Wizard is the one to use.
This one is a little bit more expensive but Text Links is great for building some high quality one way backlinks to your sites. Even if you decide not to spend money on it, you can sign up for free without a credit card and get 25 free one way backlinks as a trial. Text Links works on a credit system where a home page links costs 3 credits and a sub page link costs 1 credit. You can either pay $99/month to get 99 credits every month, and you can also buy credits at $2 each. Text Links continues to add new features and one of the nice ones is that you can actually submit your own articles with up to 3 of your own backlinks in it. These guys have 5000+ blogs so that's a ton of backlinks you can get back to your sites.
Here's a really great free backlinks service with a reasonably priced one time upgrade as well. With Social Monkee, you can sign up for free and then every day you can submit a link and get 25 backlinks from a variety of social bookmarking sites. Each of the bookmark sites are on unique domains and C class IPs. What makes this backlinking service even better is that, for a one time $47 upgrade to Social Monkee, you can submit 3 links a day and get backlinks from 100 sites for each link. With your upgraded access, they also provide you with an RSS feed for each of your submited links so you can get them pinged easily. With the 25 free a day backlinks and then low priced one-time upgrade, Social Monkee is more than worth adding into your backlinking arsenal.
SEO Blueprint is actually a group of 3 products all rolled into one for a cost of $67 a month. With SEO Blueprint, you get a backlink building tool that simply creates one way backlinks back to your sites. There's also an article submitting tool similar to UAW but your articles gets submitted to their network of blogs. You can get the article submitting tool Article Blueprint on it's own for $24.95 a month. What I feel is the best part of this though is what they're calling Blog Blueprint. Instead of writing full articles, you write up to 10 "snippets" of around 100 words with a backlink to your site in there. You submit those snippets and they get posted on a network of their blogs. Very quick and easy to do every day. You can get this tool, Blog Blueprint, on it's own for only $57.00 a month. Combine the blog blueprint tool with UAW and you have a powerfull system for generating all those backlinks.