Odoo CE lacks some features found in Enterprise. But OCA (Odoo Community Association) and individual developers maintain hundreds of modules that fill the gaps. Here are the most useful.
OCA: Odoo Community Association
An organization maintaining quality-reviewed modules on GitHub. Code is reviewed, automatically tested, and follows coding standards. It's not always perfect, but it's the best source for community modules.
web-addons
OCA/web contains interface improvements. web_responsive (mobile-friendly backend), web_environment_ribbon (shows which environment you're in: staging, production), web_export_view (export list view to Excel). Small modules that make daily life better.
server-tools
base_technical_features (hide technical menus from non-admin), auto_backup (scheduled database backup to local or FTP), base_user_role (role-based permission assignment instead of individual groups per user).
account and l10n-sweden
OCA/l10n-sweden: Swedish accounting customizations. account_financial_report: advanced financial reports missing from CE (balance sheet, P&L with comparison period). account_payment_order: batched payment runs.
reporting-engine
report_xlsx: generate Excel reports directly from Odoo. report_py3o: use LibreOffice templates (ODT, DOCX) instead of QWeb. Good if you have existing report templates in Word format.
Caution
Verify the module supports your Odoo version. Check latest commit date: a module not updated in 18 months might not work with Odoo 18. Read GitHub issues before installation. And always test in staging.