Have you tried using oktopost?
It is great for managing social media marketing on the major social networks. We use it to schedule posts and then track for engagement. As a business we have a big need for in-depth reporting and analytics of our social efforts and we are very pleased with the oktopost reporting.
Since you mentioned agencies I would suggest taking a look at Oktopost for agencies.
Since you mentioned LinkedIn, you might want to check out oktopost. I saw that they just announced a new listening feature, and I'm very happy with the rest of the functionality.
We use Oktopost. As a B2B company, we are pretty active on social, specifically LinkedIn and Twitter, and oktopost is great for posting and engaging. Not sure there is another tool that can compare when it comes to LinkedIn capabilities and I've used a few..
Oktopost is a great tool that lets you manage all of your posting to the networks you mentioned (also LI). As for analytics, they have a great metrics for engagement on your posts.
Another great tool is Oktopost, it was designed for b2b companies to manage their social media marketing. They have a free plan that is definitely worth checkin out: oktopost
You might want to look into oktopost's startup offer. Oktopost is a great tool for social media management and lead generation. They give startups free access to the platform and resources.. http://www.oktopost.com/pages/startups
Who are you marketing to? We're a b2b company, for us the the best distribution channels are LinkedIn Groups, Twitter and Google+ communities. We use a tool called Oktopost, which is great for content distribution and lead generation from social media.