The LAC has a “Genealogy and Family History” section. The website hosts databases of core records which allow for easy access to indexes of original sources: www.collectionscanada.gc.ca/lac-bac/search-recherche/anc.php?Language=eng This includes; immigration and citizenship, land, censuses, military, and vital records. Among the ones I use in my client research on a regular bases are the land petitions, land grants, marriage bonds, and especially for the Irish the immigration records to Quebec City (1865-1900) and Grosse Île (1832-1937). A word needs to be said about the Grosse Île records. These only consist of 33,026 entries and they are for the Quarantine Station. They are not passenger arrival records. However, the Irish are historically linked to both this port and especially to the Quarantine Station, so it remains an important resource. If you’re not sure which database you need, then there is a general search field.
The LAC has a large newspaper collection and what is on microfilm can be obtained through inter-library loan. They have a small but significant church records collection from different denominations. What is on microfilm can be ordered through the inter-library loan system. It is important to remember that many LAC microfilm are on file at the Family History Library (FHL): www.familysearch.org These can be ordered through their system.
As you are exploring the collections and databases of the LAC, don’t neglect the provincial archives and their databases to complement your research.