There's more we could - and probably should - be doing, but here are a few of our costs in ~5 years of home ownership.
Random purchases from Home Depot/Lowes that were extremely common over the first year (as referenced by another owner above)
$1500
Other yard care purchases - lawnmower, etc.
$500
Garage door: Spring broke. Bottom seal failed, no easy replacement (but figured something out). Opener failed. Another spring failure. Rail failed due to faulty installation of new opener.
~$1000
Sliding door and old windows replaced - most windows and one sliding door were newer, but a few were not and were getting worse and worse.
$4500
Plumbing drain line leak, resultant pest problem
$1700
Second plumbing drain line section replacement after persistent clog, tree root damage
$1200
Pest problems - traps, poison, exterminator (mostly DIY, but relied on exterminator once):
$500
Attic insulation DIY
$600
Air conditioning service (only once, not so critical where I live as in Houston)
$125
Air/water filters
$100
Cabinet repair when one fell off the wall and almost landed on me (!)
$75
Ceiling fan installation
$250
Thermostat failure and replacement
$75
Gardener (DIY for first four years, gave up last year):
$220 one-time cleanout and subsequent $100/mo.
It goes on, but you get the idea. Many DIY repairs, but certainly not all. This list doesn't include some big-ticket maintenance items that are coming at some point - repaint interior/fill cracks, repaint exterior, roof, replacement of HVAC, tenting for termites, water heater or other major appliance replacement. It also doesn't include what amounts to an enormous drain on finances that all of my homeowner friends participate in and do their best to encourage us to join in on - upgrades and remodels (Tens to $100K+).
A decent guideline is to budget 2% x the value of the structure of your house annually (different than your house price, which includes land). You'd have to budget extra if you're doing bigger upgrades and/or have a large yard to care for. Naturally, the more you DIY, the lower you can probably get your cost, but it's a lot of work.