 
If you are a small business owner and you need to get up to speed and get into the tools fast then I recommend going to SeoBook. Aaron Wall really covers the gambit of tools and makes it easy to get started building your link relationships.
1. Back Link Analyzer by Seo Book
2. Quantity & Quality of your Back Links by Back Link Watch
3. Complete Link Report by Link Diagnosis
4. Link Harvester by Seo Book
5. Link Suggestion Tool by Seo Book
6. Compare Domain Back Link History by Majestic Seo 
7. Link Assistant by Seo Spyglass
8. Page Rank Back links by Smart Page Rank
9. Link Search by Solo Seo
10. Back Links Checker by Valid Rank
11. Discover your Links by Google
12. Link Scape by Seo MozÂ
These are some paid link tools.
1. Link Building Tool by Buzz Stream
2. Hub Finder by Seo Book
3. Link Building Tools by Shoe Money
