1) Build up an entry door casing with applied moldings to create a more substantial first impression of your home.
Four 6-foot-long-by-3¾-inch-wide primed white miter-less moldings, about $80; Van Dyke's Restorers
2) Update your concrete front steps with a paint-on checkerboard pattern. Floor paint is about $25 a quart, so two colors are $50. For wood floors where the finish is damaged but the flooring in good shape, paint an area rug, a pattern, or even the whole floor - use a top quality floor paint for durability.
3) Add detail to the corners of room openings with wooden brackets, painted to the color of your trim and doors. These are about $35 each at big box hardware stores.
4) Light up your counter tops with LED lighting from Environmental Lights. Attach a concealable LED strip to the underside of your laundry, bath, kitchen and home office cabinets (don't forget to add a power driver) for about $30.
5) Dress up a small window with stained glass. If you can't fully install the new window, hang it from the ceiling with chains, in front of the existing window. This one for $69 on Ebay.
6) Add a chair rail to your dining room to get traditional archictectural detail, and an opportunity to change the paint color on only part of the wall. MDF moldings are as low as $2.00 per linear foot, making a 10' x 10' room under $100.
7) When your stairway newel post looks dated, add a finial to the top. These are solid wood for $80 each, but you can try a large resin finial for about $20.
8) Wrap a pedestal sink with a skirt and conceal your waste bin and toiletries below. Stick fabric to the basin edge with adhesive-backed Velcro.
For fabric and Velcro, and even some iron-on hem tape, you can make this for under $50.
9) Give yourself better mood lighting and energy savings by putting kitchen, bedroom, bath, and dining lighting on Lutron dimmers. They are $20-25 at most hardware stores.
10) Cover the bottoms of scuffed doors or kitchen toe kicks with stainless or brass covers. Some are readily available at hardware shops or at Doors2me.