Soccerway
* Exhaustive calendar of games by future date
* Worldwide league data covering 1,482 global leagues, 89 continental competitions and every national team
* Easy-to-read squad data
* Result info presented in helpful colour-coding
Soccerbase
* Player appearance data in handy list form, with brief statistics
* Performance data with/without certain players (up to two using ‘player filter’)
Wikipedia
* The best season-by-season breakdown around, often including position after each match, colour-coded W/D/L and appearance data
Whoscored
* Strength and weakness assessment of each team, which can guide more detailed scrutiny.
* Formation summary for each club. The ‘squad list’ option shows which players have played in which position and how often.
* Detailed team data in and intra-league comparison, broken down into shot zones, accuracy, body part, key passes, pass length, fouls, passes dribbles etc
* Detailed player data within teams and intra-league, again broken down into shot zones, accuracy, body part, key passes, pass length, fouls, passes dribbles etc
Fbref
* The most detailed player performance data available for free, including things you don’t get anywhere else.
11v11
* League table generator for any date (English leagues only)
* Club’s record against another team (with match data)
* Club appearance data season-by-season
Soccerstats
* Useful league stats (for lots of European leagues), with a few examples that you can’t find easily elsewhere: records when scoring and conceding first, goals per 10/15 minutes, time spent leading/trailing
* Handy club information of results against other clubs by league position:
Transfermarkt
* All transfers in a club’s history (occasionally beware the often slightly off values)
* Some unique insights: attacking partnerships, youngest/oldest players by season, youngest/oldest average XIs, players’ penalty records
* Creation of custom tables (choose your clubs and your seasons and create table)
* Managers’ records against other managers and clubs and their most-used players
Worldfootball.net
* Great historical database of worldwide squads and games
* View clubs by historical season squad list and results plus A-Z historical player list
* Great lineup information for old matches (although only goes back so far) using the historical results
Foot Stats
* The best referee database I’ve found (English leagues only)
OTHER WEBSITES
Bdfutbol - Reams of information (present and historical) on domestic leagues and clubs across Europe.
Rsssf - The bible of historic league tables and competition history worldwide. Functional design, exhaustive content